Forces are interactions that can cause changes in an object's motion. A force is a vector quantity that has both magnitude and direction. Force diagrams use arrows to represent force vectors and their directions. Free-body diagrams isolate a single object and show only the forces acting on that object, ignoring external interactions. Understanding forces through force and free-body diagrams helps analyze situations involving changes to objects' motion, such as collisions.
Have a data in the form of required information in descriptive form.And learn to know how newtons's laws of motion are applicable in different phenomena-----------------------------'--'---'---'''''''-----------------------------------
- The document discusses Newton's laws of motion and forces.
- Newton's first law states that an object will remain at rest or in uniform motion unless acted upon by a net force. The second law relates the net force on an object to its acceleration. The third law states that for every action force there is an equal and opposite reaction force.
- A force is defined as an interaction between two bodies or a body and its environment. Forces can be contact forces like normal forces or long-range forces like gravity. Forces are represented as vectors with magnitude and direction.
The sand increases the coefficient of friction between the tires of a car and the road, making it safer to drive on icy roads. Therefore, the correct answer is 2.
The forces acting on the box are:
1. Applied force (Fa) by the boy pulling the rope towards the right.
2. Frictional force (Ff) by the floor on the box opposing the motion towards the left.
3. Normal force (Fn) by the floor on the box perpendicular to the surface.
To determine the resultant force, we add the forces acting on the same line of action (towards the right and left).
Fa - Ff = Resultant force
Since Fa is greater than Ff, the resultant force is towards the right. Therefore, the box will accelerate towards the right direction as the net force is unbalanced to the right.
In physics, a force is any interaction which tends to change the motion of an object.
In other words, a force can cause an object with mass to change its velocity (which includes to begin moving from a state of rest), i.e., to accelerate.
Force can also be described by intuitive concepts such as a push or a pull.
A force has both magnitude and direction, making it a vector quantity. It is measured in the SI unit of newtons and represented by the symbol F.
The original form of Newton's second law states that the net force acting upon an object is equal to the rate at which its momentum changes with time.
If the mass of the object is constant, this law implies that the acceleration of an object is directly proportional to the net force acting on the object, is in the direction of the net force, and is inversely proportional to the mass of the object.
As a formula, this is expressed as:
Related concepts to force include: thrust, which increases the velocity of an object; drag, which decreases the velocity of an object; and torque which produces changes in rotational speed of an object. In an extended body, each part usually applies forces on the adjacent parts; the distribution of such forces through the body is the so-called mechanical stress.
Pressure is a simple type of stress. Stress usually causes deformation of solid materials, or flow in fluids.
Aristotle famously described a force
Static force analysis examines forces on structures when inertia forces are negligible compared to external forces. The document defines types of forces like tension, compression, and shear. It also discusses Newton's laws of motion, equilibrium conditions for 2-force and 3-force systems, and constructing free body diagrams to isolate individual parts. Moment of inertia and inertia forces are introduced, along with applying principles like D'Alembert's to dynamic force analysis when inertia forces are significant.
This document discusses the concept of forces in physics. It defines a force as a push or pull on an object and explains that forces are vectors that have both magnitude and direction. There are four main forces in nature: gravity, electromagnetism, the strong nuclear force, and the weak nuclear force. Dynamics and statics are introduced as areas of study related to forces and motion. Newton's three laws of motion are outlined. Common ways of measuring mass and examples of force problems are provided, including free body diagrams, friction, inclined planes, and pulleys.
Forces can cause objects to move, change speed or direction, turn, bend or twist. Forces can be contact forces that act through direct physical contact, like pushing or pulling, or non-contact forces that act over a distance, like magnetism or gravity. Balanced forces cause no change in motion, while unbalanced forces cause acceleration or changes in speed or direction. Newton's three laws of motion describe how forces affect the motion of objects.
Have a data in the form of required information in descriptive form.And learn to know how newtons's laws of motion are applicable in different phenomena-----------------------------'--'---'---'''''''-----------------------------------
- The document discusses Newton's laws of motion and forces.
- Newton's first law states that an object will remain at rest or in uniform motion unless acted upon by a net force. The second law relates the net force on an object to its acceleration. The third law states that for every action force there is an equal and opposite reaction force.
- A force is defined as an interaction between two bodies or a body and its environment. Forces can be contact forces like normal forces or long-range forces like gravity. Forces are represented as vectors with magnitude and direction.
The sand increases the coefficient of friction between the tires of a car and the road, making it safer to drive on icy roads. Therefore, the correct answer is 2.
The forces acting on the box are:
1. Applied force (Fa) by the boy pulling the rope towards the right.
2. Frictional force (Ff) by the floor on the box opposing the motion towards the left.
3. Normal force (Fn) by the floor on the box perpendicular to the surface.
To determine the resultant force, we add the forces acting on the same line of action (towards the right and left).
Fa - Ff = Resultant force
Since Fa is greater than Ff, the resultant force is towards the right. Therefore, the box will accelerate towards the right direction as the net force is unbalanced to the right.
In physics, a force is any interaction which tends to change the motion of an object.
In other words, a force can cause an object with mass to change its velocity (which includes to begin moving from a state of rest), i.e., to accelerate.
Force can also be described by intuitive concepts such as a push or a pull.
A force has both magnitude and direction, making it a vector quantity. It is measured in the SI unit of newtons and represented by the symbol F.
The original form of Newton's second law states that the net force acting upon an object is equal to the rate at which its momentum changes with time.
If the mass of the object is constant, this law implies that the acceleration of an object is directly proportional to the net force acting on the object, is in the direction of the net force, and is inversely proportional to the mass of the object.
As a formula, this is expressed as:
Related concepts to force include: thrust, which increases the velocity of an object; drag, which decreases the velocity of an object; and torque which produces changes in rotational speed of an object. In an extended body, each part usually applies forces on the adjacent parts; the distribution of such forces through the body is the so-called mechanical stress.
Pressure is a simple type of stress. Stress usually causes deformation of solid materials, or flow in fluids.
Aristotle famously described a force
Static force analysis examines forces on structures when inertia forces are negligible compared to external forces. The document defines types of forces like tension, compression, and shear. It also discusses Newton's laws of motion, equilibrium conditions for 2-force and 3-force systems, and constructing free body diagrams to isolate individual parts. Moment of inertia and inertia forces are introduced, along with applying principles like D'Alembert's to dynamic force analysis when inertia forces are significant.
This document discusses the concept of forces in physics. It defines a force as a push or pull on an object and explains that forces are vectors that have both magnitude and direction. There are four main forces in nature: gravity, electromagnetism, the strong nuclear force, and the weak nuclear force. Dynamics and statics are introduced as areas of study related to forces and motion. Newton's three laws of motion are outlined. Common ways of measuring mass and examples of force problems are provided, including free body diagrams, friction, inclined planes, and pulleys.
Forces can cause objects to move, change speed or direction, turn, bend or twist. Forces can be contact forces that act through direct physical contact, like pushing or pulling, or non-contact forces that act over a distance, like magnetism or gravity. Balanced forces cause no change in motion, while unbalanced forces cause acceleration or changes in speed or direction. Newton's three laws of motion describe how forces affect the motion of objects.
5-1 NEWTON’S FIRST AND SECOND LAWS
After reading this module, you should be able to . . .
5.01 Identify that a force is a vector quantity and thus has
both magnitude and direction and also components.
5.02 Given two or more forces acting on the same particle,
add the forces as vectors to get the net force.
5.03 Identify Newton’s first and second laws of motion.
5.04 Identify inertial reference frames.
5.05 Sketch a free-body diagram for an object, showing the
object as a particle and drawing the forces acting on it as
vectors with their tails anchored on the particle.
5.06 Apply the relationship (Newton’s second law) between
the net force on an object, the mass of the object, and the
acceleration produced by the net force.
5.07 Identify that only external forces on an object can cause
the object to accelerate.
5-2 SOME PARTICULAR FORCES
After reading this module, you should be able to . . .
5.08 Determine the magnitude and direction of the gravitational force acting on a body with a given mass, at a location
with a given free-fall acceleration.
5.09 Identify that the weight of a body is the magnitude of the
net force required to prevent the body from falling freely, as
measured from the reference frame of the ground.
5.10 Identify that a scale gives an object’s weight when the
measurement is done in an inertial frame but not in an accelerating frame, where it gives an apparent weight.
5.11 Determine the magnitude and direction of the normal
force on an object when the object is pressed or pulled
onto a surface.
5.12 Identify that the force parallel to the surface is a frictional
the force that appears when the object slides or attempts to
slide along the surface.
5.13 Identify that a tension force is said to pull at both ends of
a cord (or a cord-like object) when the cord is taut. etc...
Here are the reaction forces described for each example:
a. The ball exerts a force of 500 N [South] on the football player's foot.
b. The table exerts an equal and opposite force of 25 N [up] on the book.
c. The bullet exerts a force of 1,000 N [West] on the gun.
d. The earth exerts a force of 5 N [up] on the apple.
The document discusses Newton's laws of motion, including the definition of force, units of measurement for force, types of forces like friction and gravity, and Newton's three laws of motion - the law of inertia, the law of acceleration (F=ma), and the law of interaction (action-reaction forces). It provides examples and explanations of these fundamental physics concepts relating to force and motion.
Newton's laws of motion describe the relationship between an object and the forces acting upon it, and its motion in response to those forces. The three laws are: 1) An object at rest stays at rest and an object in motion stays in motion unless acted upon by an unbalanced force. 2) The acceleration of an object as produced by a net force is directly proportional to the magnitude of the net force, in the direction of the net force. 3) For every action, there is an equal and opposite reaction.
The document discusses Isaac Newton's three laws of motion. Newton's first law states that an object at rest stays at rest and an object in motion stays in motion unless acted upon by an unbalanced force. Newton's second law relates that the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass. Newton's third law states that for every action there is an equal and opposite reaction.
This document summarizes key concepts from Chapter 4 of a college physics textbook, including Newton's laws of motion. It discusses concepts like force, mass, inertia, gravity, friction, and how forces cause motion and determine acceleration. Examples are provided to illustrate applying Newton's laws to solve problems involving forces like tension, normal force, gravitational force, and static/kinetic friction. The document also discusses how forces like air resistance impact a falling object's motion.
The document outlines a 12 lesson plan on the topic of forces and motion. It will cover key concepts such as forces in different directions, how objects start to move, friction, reaction of surfaces, speed, modeling motion, force interactions, changes in momentum, car safety, and laws of motion. Each lesson will include objectives, activities, literacy and numeracy focuses, and questions to help students understand the key topics being covered.
The document discusses concepts related to motion and forces. It begins by defining motion as an object's change in position relative to a reference point. Speed is defined as the distance traveled divided by time, while velocity must include a reference direction. Forces are described as pushes or pulls that can change an object's motion. Friction and gravity are identified as important forces that oppose motion and attract objects with mass, respectively. Newton's law of universal gravitation explains the relationships between gravitational force, mass, and distance.
Newton's second law of motion states that the acceleration of an object is directly proportional to the net force acting on the object and inversely proportional to its mass. It can be expressed by the equation a=Fnet/m, where a is acceleration, Fnet is the net force, and m is mass. Newton's third law, the law of interaction, states that for every action there is an equal and opposite reaction - forces between objects always occur in action-reaction pairs. Examples include a swimmer pushing water back being pushed forward by the water in return, and a golf club hitting a ball also being hit back by the ball.
This document provides self-learning material on forces and pressure. It contains definitions of key terms like force, pressure, contact forces, non-contact forces. It describes how forces can cause objects to move, change speed or direction of motion. Experiments are presented to demonstrate that forces can also change the shape of objects. Specific forces like muscular force, magnetic force, electrostatic force, atmospheric pressure are discussed. Diagrams and activities help explain these concepts.
1) Newton's laws of motion describe the relationship between the forces acting on a body and its motion. The first law states that a body at rest stays at rest or a body in motion stays in motion with the same speed and in the same direction unless acted upon by an external force. The second law states that the acceleration of a body is directly proportional to the net force acting on it, and inversely proportional to its mass. The third law states that for every action, there is an equal and opposite reaction.
2) Friction is a force that opposes the motion of objects that are moving or attempting to move past each other. The coefficient of static friction determines the maximum frictional force that can develop before
Week 2 OverviewLast week, we studied the relationship between .docxmelbruce90096
Week 2 Overview
Last week, we studied the relationship between acceleration, velocity, displacement, and time. Acceleration in an object is caused by the force acting on it. This week, we'll study the relationship between force and acceleration. Central to this study are the laws of motion that Isaac Newton discovered in the 17th century.
You must have observed in daily life that when you apply brakes to a car, it takes some time before the car stops completely. The speed with which a train moves depends on the amount of force applied by the engine. A ball thrown at a wall bounces back. Newton's laws help you understand the motion of day-to-day objects and explain all this phenomena. These laws can also help you create realistic graphic animations!
Have you ever walked on slippery surfaces? If so, you would have realized how difficult it is to walk on them. Slippery surfaces have less friction, which makes it difficult to walk. In fact, surface transportation would be impossible without friction. This week, we take a closer look at this important force. We will use Newton's laws to analyze problems involving friction.
Newton’s First Law
What are Forces?
Forces are the result of the interaction between bodies. In simple words, a force is the push or pull acting on an object. For example, you exert a force on a rope to pull an object, and the rope pulls the object.
Here, we need a transition between the definition of forces and Newton’s Laws. We also need a couple of examples of how to draw a force diagram.
The Law of Inertia
Newton's first law of motion explains the relation between the force applied on an object and its motion.
The law states that:
An object continues to remain in a state of rest or of uniform motion in a straight line unless compelled by an external force to act otherwise.
This means that an object prefers to remain in a state of rest or uniform motion; in order to change the state it's in you need to apply force to it. Further, an object will always resist the force applied to it. The property of an object to resist an external force is called inertia, and for this reason, Newton's first law is called the law of inertia.
If you slide an object on a smooth floor with a given speed, the distance it moves depends upon the friction between the object and the floor. The smoother the floor, the greater the distance traveled by the object. The object eventually stops because of the external force of friction.
A force is required to change the velocity of a body. To understand this statement first recall from your study of kinematics that velocity is a vector with a magnitude (speed) and a direction. In the absence of a force, both speed and direction are constant. When a force acts on an object, it changes the speed, direction, or both of the objects.
There is no basic difference between an object at rest and an object in uniform motion; rest and uniform motion are relative terms. An object at rest with respec.
1) A force is a push or pull that can be measured in Newtons. Forces can combine and act in the same or opposite directions. Friction is a force that slows or prevents motion and depends on surface roughness and weight.
2) Gravity is the force of attraction between objects with mass. Newton's three laws of motion describe how forces affect motion. An object at rest or in motion stays at rest or in motion unless acted upon by an unbalanced force. The greater the mass of an object, the greater the force needed to accelerate or decelerate it. For every action force, there is an equal and opposite reaction force.
3) Centripetal force pulls objects toward the center of a
Ekeeda Provides Online Civil Engineering Degree Subjects Courses, Video Lectures for All Engineering Universities. Video Tutorials Covers Subjects of Mechanical Engineering Degree.
Learn Online Courses of Subject Engineering Mechanics of First Year Engineering. Clear the Concepts of Engineering Mechanics Through Video Lectures and PDF Notes. Visit us: https://ekeeda.com/streamdetails/subject/Engineering-Mechanics
Learn Online Courses of Subject Engineering Mechanics of First Year Engineering. Clear the Concepts of Engineering Mechanics Through Video Lectures and PDF Notes. Visit us: https://ekeeda.com/streamdetails/subject/Engineering-Mechanics
There are several types of common forces in mechanics. Contact forces require direct contact between objects and include tension, friction, spring forces, and drag forces. Friction includes static, kinetic, and rolling varieties. Non-contact forces act at a distance and include gravitational and electromagnetic forces. Pseudo forces do not exist physically but arise due to perspective in accelerated frames of reference. Understanding these various forces is essential for mechanics problems.
This document provides an overview of force and dynamics concepts. It defines dynamics as the branch of mechanics dealing with the causes of motion. Key topics covered include forces and their effects, free body diagrams, Newton's laws of motion, momentum and its conservation, impulse, different types of forces including gravity, drag, friction, tension, and spring forces. It also discusses work, power, energy, and their transformations. Force is defined as what can change an object's state of motion. Dynamics principles are applied to examples like a man on a sloping table and collisions.
This document provides an introduction to engineering mechanics from Baba Farid College of Engineering and Technology. It includes:
1) Biographical information about the instructor Parvinkal Singh Mann, who has worked in engineering education for many years and published over 20 research papers.
2) An overview of engineering mechanics, which involves the study of forces and their effects on bodies at rest (statics) and in motion (dynamics), and how it relates to other fields like kinematics and kinetics.
3) Definitions of key terms in mechanics like force, pressure, mass, weight, density, and others, and explanations of the differences between concepts like mass and weight.
The document discusses collisions and the law of conservation of momentum. It provides examples of how to use a momentum table and algebra to solve for unknown velocities in collision problems involving isolated systems where momentum is conserved. Specifically, it works through examples of a person catching a medicine ball on ice and of two people colliding on an ice rink to determine their combined velocity after collision.
Gravity The importance of Gravity What if gravity is too strongMervatMarji2
Directly proportional to the product of the masses of the objects being attracted
Inversely proportional to the distance between the objects squared
𝐹=𝐺 𝑚1𝑚2/𝑑^2
5-1 NEWTON’S FIRST AND SECOND LAWS
After reading this module, you should be able to . . .
5.01 Identify that a force is a vector quantity and thus has
both magnitude and direction and also components.
5.02 Given two or more forces acting on the same particle,
add the forces as vectors to get the net force.
5.03 Identify Newton’s first and second laws of motion.
5.04 Identify inertial reference frames.
5.05 Sketch a free-body diagram for an object, showing the
object as a particle and drawing the forces acting on it as
vectors with their tails anchored on the particle.
5.06 Apply the relationship (Newton’s second law) between
the net force on an object, the mass of the object, and the
acceleration produced by the net force.
5.07 Identify that only external forces on an object can cause
the object to accelerate.
5-2 SOME PARTICULAR FORCES
After reading this module, you should be able to . . .
5.08 Determine the magnitude and direction of the gravitational force acting on a body with a given mass, at a location
with a given free-fall acceleration.
5.09 Identify that the weight of a body is the magnitude of the
net force required to prevent the body from falling freely, as
measured from the reference frame of the ground.
5.10 Identify that a scale gives an object’s weight when the
measurement is done in an inertial frame but not in an accelerating frame, where it gives an apparent weight.
5.11 Determine the magnitude and direction of the normal
force on an object when the object is pressed or pulled
onto a surface.
5.12 Identify that the force parallel to the surface is a frictional
the force that appears when the object slides or attempts to
slide along the surface.
5.13 Identify that a tension force is said to pull at both ends of
a cord (or a cord-like object) when the cord is taut. etc...
Here are the reaction forces described for each example:
a. The ball exerts a force of 500 N [South] on the football player's foot.
b. The table exerts an equal and opposite force of 25 N [up] on the book.
c. The bullet exerts a force of 1,000 N [West] on the gun.
d. The earth exerts a force of 5 N [up] on the apple.
The document discusses Newton's laws of motion, including the definition of force, units of measurement for force, types of forces like friction and gravity, and Newton's three laws of motion - the law of inertia, the law of acceleration (F=ma), and the law of interaction (action-reaction forces). It provides examples and explanations of these fundamental physics concepts relating to force and motion.
Newton's laws of motion describe the relationship between an object and the forces acting upon it, and its motion in response to those forces. The three laws are: 1) An object at rest stays at rest and an object in motion stays in motion unless acted upon by an unbalanced force. 2) The acceleration of an object as produced by a net force is directly proportional to the magnitude of the net force, in the direction of the net force. 3) For every action, there is an equal and opposite reaction.
The document discusses Isaac Newton's three laws of motion. Newton's first law states that an object at rest stays at rest and an object in motion stays in motion unless acted upon by an unbalanced force. Newton's second law relates that the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass. Newton's third law states that for every action there is an equal and opposite reaction.
This document summarizes key concepts from Chapter 4 of a college physics textbook, including Newton's laws of motion. It discusses concepts like force, mass, inertia, gravity, friction, and how forces cause motion and determine acceleration. Examples are provided to illustrate applying Newton's laws to solve problems involving forces like tension, normal force, gravitational force, and static/kinetic friction. The document also discusses how forces like air resistance impact a falling object's motion.
The document outlines a 12 lesson plan on the topic of forces and motion. It will cover key concepts such as forces in different directions, how objects start to move, friction, reaction of surfaces, speed, modeling motion, force interactions, changes in momentum, car safety, and laws of motion. Each lesson will include objectives, activities, literacy and numeracy focuses, and questions to help students understand the key topics being covered.
The document discusses concepts related to motion and forces. It begins by defining motion as an object's change in position relative to a reference point. Speed is defined as the distance traveled divided by time, while velocity must include a reference direction. Forces are described as pushes or pulls that can change an object's motion. Friction and gravity are identified as important forces that oppose motion and attract objects with mass, respectively. Newton's law of universal gravitation explains the relationships between gravitational force, mass, and distance.
Newton's second law of motion states that the acceleration of an object is directly proportional to the net force acting on the object and inversely proportional to its mass. It can be expressed by the equation a=Fnet/m, where a is acceleration, Fnet is the net force, and m is mass. Newton's third law, the law of interaction, states that for every action there is an equal and opposite reaction - forces between objects always occur in action-reaction pairs. Examples include a swimmer pushing water back being pushed forward by the water in return, and a golf club hitting a ball also being hit back by the ball.
This document provides self-learning material on forces and pressure. It contains definitions of key terms like force, pressure, contact forces, non-contact forces. It describes how forces can cause objects to move, change speed or direction of motion. Experiments are presented to demonstrate that forces can also change the shape of objects. Specific forces like muscular force, magnetic force, electrostatic force, atmospheric pressure are discussed. Diagrams and activities help explain these concepts.
1) Newton's laws of motion describe the relationship between the forces acting on a body and its motion. The first law states that a body at rest stays at rest or a body in motion stays in motion with the same speed and in the same direction unless acted upon by an external force. The second law states that the acceleration of a body is directly proportional to the net force acting on it, and inversely proportional to its mass. The third law states that for every action, there is an equal and opposite reaction.
2) Friction is a force that opposes the motion of objects that are moving or attempting to move past each other. The coefficient of static friction determines the maximum frictional force that can develop before
Week 2 OverviewLast week, we studied the relationship between .docxmelbruce90096
Week 2 Overview
Last week, we studied the relationship between acceleration, velocity, displacement, and time. Acceleration in an object is caused by the force acting on it. This week, we'll study the relationship between force and acceleration. Central to this study are the laws of motion that Isaac Newton discovered in the 17th century.
You must have observed in daily life that when you apply brakes to a car, it takes some time before the car stops completely. The speed with which a train moves depends on the amount of force applied by the engine. A ball thrown at a wall bounces back. Newton's laws help you understand the motion of day-to-day objects and explain all this phenomena. These laws can also help you create realistic graphic animations!
Have you ever walked on slippery surfaces? If so, you would have realized how difficult it is to walk on them. Slippery surfaces have less friction, which makes it difficult to walk. In fact, surface transportation would be impossible without friction. This week, we take a closer look at this important force. We will use Newton's laws to analyze problems involving friction.
Newton’s First Law
What are Forces?
Forces are the result of the interaction between bodies. In simple words, a force is the push or pull acting on an object. For example, you exert a force on a rope to pull an object, and the rope pulls the object.
Here, we need a transition between the definition of forces and Newton’s Laws. We also need a couple of examples of how to draw a force diagram.
The Law of Inertia
Newton's first law of motion explains the relation between the force applied on an object and its motion.
The law states that:
An object continues to remain in a state of rest or of uniform motion in a straight line unless compelled by an external force to act otherwise.
This means that an object prefers to remain in a state of rest or uniform motion; in order to change the state it's in you need to apply force to it. Further, an object will always resist the force applied to it. The property of an object to resist an external force is called inertia, and for this reason, Newton's first law is called the law of inertia.
If you slide an object on a smooth floor with a given speed, the distance it moves depends upon the friction between the object and the floor. The smoother the floor, the greater the distance traveled by the object. The object eventually stops because of the external force of friction.
A force is required to change the velocity of a body. To understand this statement first recall from your study of kinematics that velocity is a vector with a magnitude (speed) and a direction. In the absence of a force, both speed and direction are constant. When a force acts on an object, it changes the speed, direction, or both of the objects.
There is no basic difference between an object at rest and an object in uniform motion; rest and uniform motion are relative terms. An object at rest with respec.
1) A force is a push or pull that can be measured in Newtons. Forces can combine and act in the same or opposite directions. Friction is a force that slows or prevents motion and depends on surface roughness and weight.
2) Gravity is the force of attraction between objects with mass. Newton's three laws of motion describe how forces affect motion. An object at rest or in motion stays at rest or in motion unless acted upon by an unbalanced force. The greater the mass of an object, the greater the force needed to accelerate or decelerate it. For every action force, there is an equal and opposite reaction force.
3) Centripetal force pulls objects toward the center of a
Ekeeda Provides Online Civil Engineering Degree Subjects Courses, Video Lectures for All Engineering Universities. Video Tutorials Covers Subjects of Mechanical Engineering Degree.
Learn Online Courses of Subject Engineering Mechanics of First Year Engineering. Clear the Concepts of Engineering Mechanics Through Video Lectures and PDF Notes. Visit us: https://ekeeda.com/streamdetails/subject/Engineering-Mechanics
Learn Online Courses of Subject Engineering Mechanics of First Year Engineering. Clear the Concepts of Engineering Mechanics Through Video Lectures and PDF Notes. Visit us: https://ekeeda.com/streamdetails/subject/Engineering-Mechanics
There are several types of common forces in mechanics. Contact forces require direct contact between objects and include tension, friction, spring forces, and drag forces. Friction includes static, kinetic, and rolling varieties. Non-contact forces act at a distance and include gravitational and electromagnetic forces. Pseudo forces do not exist physically but arise due to perspective in accelerated frames of reference. Understanding these various forces is essential for mechanics problems.
This document provides an overview of force and dynamics concepts. It defines dynamics as the branch of mechanics dealing with the causes of motion. Key topics covered include forces and their effects, free body diagrams, Newton's laws of motion, momentum and its conservation, impulse, different types of forces including gravity, drag, friction, tension, and spring forces. It also discusses work, power, energy, and their transformations. Force is defined as what can change an object's state of motion. Dynamics principles are applied to examples like a man on a sloping table and collisions.
This document provides an introduction to engineering mechanics from Baba Farid College of Engineering and Technology. It includes:
1) Biographical information about the instructor Parvinkal Singh Mann, who has worked in engineering education for many years and published over 20 research papers.
2) An overview of engineering mechanics, which involves the study of forces and their effects on bodies at rest (statics) and in motion (dynamics), and how it relates to other fields like kinematics and kinetics.
3) Definitions of key terms in mechanics like force, pressure, mass, weight, density, and others, and explanations of the differences between concepts like mass and weight.
The document discusses collisions and the law of conservation of momentum. It provides examples of how to use a momentum table and algebra to solve for unknown velocities in collision problems involving isolated systems where momentum is conserved. Specifically, it works through examples of a person catching a medicine ball on ice and of two people colliding on an ice rink to determine their combined velocity after collision.
Gravity The importance of Gravity What if gravity is too strongMervatMarji2
Directly proportional to the product of the masses of the objects being attracted
Inversely proportional to the distance between the objects squared
𝐹=𝐺 𝑚1𝑚2/𝑑^2
Use the given information and the theorems you have learned to show that r || s.
A carpenter is creating a woodwork pattern and wants two long pieces to be parallel. m1= (8x + 20)° and m2 = (2x + 10)°. If x = 15, show that pieces A and B are parallel.
Recall that the converse of a theorem is found by exchanging the hypothesis and conclusion. The converse of a theorem is not automatically true. If it is true, it must be stated as a postulate or proved as a separate theorem.
Refer to the diagram. Use the given information and the theorems you have learned to show that r || s.
What if…? Suppose the corresponding angles on the opposite side of the boat measure (4y – 2)° and (3y + 6)°, where
y = 8. Show that the oars are parallel
A line through the center of the horizontal piece forms a transversal to pieces A and B.
Use the given information and the theorems you have learned to show that r || s.
Use the given information and the theorems you have learned to show that r || s.
A carpenter is creating a woodwork pattern and wants two long pieces to be parallel. m1= (8x + 20)° and m2 = (2x + 10)°. If x = 15, show that pieces A and B are parallel.
Recall that the converse of a theorem is found by exchanging the hypothesis and conclusion. The converse of a theorem is not automatically true. If it is true, it must be stated as a postulate or proved as a separate theorem.
Refer to the diagram. Use the given information and the theorems you have learned to show that r || s.
What if…? Suppose the corresponding angles on the opposite side of the boat measure (4y – 2)° and (3y + 6)°, where
y = 8. Show that the oars are parallel
A line through the center of the horizontal piece forms a transversal to pieces A and B.
Use the given information and the theorems you have learned to show that r || s.
Use the given information and the theorems you have learned to show that r || s.
A carpenter is creating a woodwork pattern and wants two long pieces to be parallel. m1= (8x + 20)° and m2 = (2x + 10)°. If x = 15, show that pieces A and B are parallel.
Recall that the converse of a theorem is found by exchanging the hypothesis and conclusion. The converse of a theorem is not automatically true. If it is true, it must be stated as a postulate or proved as a separate theorem.
Refer to the diagram. Use the given information and the theorems you have learned to show that r || s.
What if…? Suppose the corresponding angles on the opposite side of the boat measure (4y – 2)° and (3y + 6)°, where
y = 8. Show that the oars are parallel
A line through the center of the horizontal piece forms a transversal to pieces A and B.
Use the given information and the theorems you have learned to show that r || s.
Use the given information and the theorems you have learned to show that r || s.
A carpenter is creating a woodwork pattern and wants two long pieces to be parallel. m1= (8x + 20)° and m2 = (2x + 10)°. If x = 15, show that pieces A and B are parallel.
Recall that the conver
hssb0704t_powerpresDNA as the transforming principle..pptMervatMarji2
Avery performed three tests on the transforming principle.
Qualitative tests showed DNA was present.
Chemical tests showed the chemical makeup matched that of DNA.
Enzyme tests showed only DNA-degrading enzymes stopped transformation.
Hershey and Chase confirm that DNA is the genetic material.
• Hershey and Chase studied viruses that infect bacteria, called bacteriophages.
• Tagged DNA was found inside the bacteria; tagged proteins were not.
They tagged viral DNA with radioactive phosphorus.
They tagged viral proteins with radioactive sulfur.
• Tagged DNA was found inside the bacteria; tagged proteins were not.
DNA structure is the same in all organisms.
• DNA is composed of four types of nucleotides.
• DNA is made up of a long chain of nucleotides.
Each nucleotide has three parts:
₋ a phosphate group.
₋ a deoxyribose sugar.
₋ a nitrogen-containing base
The nitrogen containing bases are the only difference in the four nucleotides.
Scientists Chargaff found:
The amount of adenine in an organism approximately equals the amount of thymine.
The amount of cytosine roughly equals the amount of guanine.
A=T C=G Chargaff’s rules
Watson and Crick determined the three-dimensional structure of DNA by building models.
They realized that DNA is a double helix that is made up of a sugar-phosphate backbone on the outside
with bases on the inside.
Watson and Crick’s discovery was built on the work of Rosalind Franklin and Erwin Chargaff.
₋ Franklin’s x-ray images suggested that DNA was a double helix of even width.
₋ Chargaff’s rules stated that A=T and C=G.
Nucleotides always pair in the same way.
The base-pairing rules show how nucleotides always pair up in DNA.
Because a pyrimidine (single ring) pairs with a purine (double ring), the helix has a uniform width.
A pairs with T
C pairs with G
The backbone is connected by covalent bonds.
The bases are connected by hydrogen bonds.
• Proteins carry out the process of replication.
• DNA serves only as a template.
• Enzymes and other proteins do the actual work of replication.
₋ Enzymes unzip the double helix.
₋ Free-floating nucleotides form hydrogen bonds with the template strand.
₋ DNA polymerase enzymes bond the nucleotides together to form the double helix.
₋ Polymerase enzymes form covalent bonds between nucleotides in the new strand.
₋ Two new molecules of DNA are formed, each with an original strand and a newly formed strand.
• Two new molecules of DNA are formed, each with an original strand and a newly formed strand.
• DNA replication is semiconservative.
Replication is fast and accurate.
DNA replication starts at many points in eukaryotic chromosomes.
There are many origins of replication in eukaryotic chromosomes.
DNA polymerases can find and correct err
This document provides information about the contributors and reviewers involved in creating a physics textbook. It lists the names and affiliations of the writing contributors, laboratory reviewers who tested experiments, academic reviewers from various universities, and teacher reviewers from high schools. It also acknowledges their contributions and thanks them for their support in developing the textbook.
This document is the teacher's solutions manual for the Holt Physics textbook. It contains copyright information for Holt, Rinehart and Winston, the publisher, and details that the materials are not to be resold. The solutions are organized into two sections - the first section provides solutions to problems in the student edition textbook chapters, while the second section provides solutions to problems in the problem workbook. The manual contains solutions for all 22 chapters of the textbook and their respective appendices, covering the full range of high school physics content.
This document is a chapter test from an introductory physics textbook. It covers various topics in physics including mechanics, measurements, scientific method, and models. The test contains multiple choice, short answer, and problem solving questions assessing student understanding of concepts like motion, force, energy, and measurements. It provides the questions, units, and figures/graphs referenced in the questions. The test was downloaded from an online study site by a student for their Memorial University of Newfoundland introductory physics course.
1. The document is a physics problem workbook containing multiple problems related to motion in one dimension, average velocity, average acceleration, and metric prefixes.
2. Problem A involves calculating the time it would take a sailfish messenger to deliver a message 16 km across water traveling at 120 km/h.
3. Additional practice problems calculate speeds, distances, times, and conversions between metric prefix units for scenarios involving plants, animals, transportation and other physical phenomena.
Newton's first law states that an object will remain at rest or in constant motion unless acted upon by an external force. Newton's second law relates the net force on an object to its acceleration. Newton's third law states that for every action force there is an equal and opposite reaction force. This chapter provides examples of applying Newton's laws to calculate accelerations and tensions in strings for simple systems involving masses, surfaces, and strings. Free-body diagrams are used to represent the forces acting on objects.
Newton's second law states that the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass. The net force equals mass times acceleration. Newton's third law states that for every action force exerted on one object by another, there is an equal but opposite reaction force. Action and reaction forces always occur simultaneously between interacting objects and are equal in magnitude but opposite in direction.
This document provides an overview of the Holt Physics textbook and accompanying section review workbook. It begins with instructions on how to navigate and print from the book. The majority of the document then lists the chapter and section titles covered in the textbook, along with the corresponding page numbers and exercise types contained in the section review workbook. These exercise types include concept reviews, math skills, diagram skills, and mixed reviews. The document copyright is also provided.
The document describes a problem involving drawing free-body diagrams. It provides details of forces acting on a canoe carrying a park ranger. The forces are the ranger's weight, the canoe's weight, and an upward force from the water. The solution involves drawing the canoe, and adding arrows to represent each force acting on the canoe, resulting in a completed free-body diagram. Additional practice problems then involve drawing free-body diagrams for a skydiver, sack of flour, and toy being pushed along the floor.
The document is a practice exam for a Physics I Honors course covering forces and Newton's laws of motion. It contains 26 multiple choice and free response questions testing concepts such as force, Newton's laws, friction, and kinematics. The questions provide scenarios involving objects like cars, boxes, and balloons, asking test-takers to identify forces, draw free-body diagrams, and solve for quantities like acceleration and force given mass and other values.
Newton's First Law states that an object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force. It refers to the net force on an object, which is the sum of all forces acting on it. If the net force is zero, the object is in equilibrium and its velocity will not change.
Modern Biology. Chapter Tests with Answer Key General and Advanced (3).pdfMervatMarji2
This document contains a chapter test on modern biology with multiple choice and short answer questions. It covers several topics:
1. Questions assess key terms like metabolism, magnification, organ, and reproduction. Students must match definitions to terms.
2. Multiple choice questions test understanding of concepts such as what living things need to maintain internal organization, the role of reproduction, and the driving force of evolution.
3. Short answer questions require listing major biology themes, characteristics of life, and explaining scientific methods and measurements.
4. A graph is provided assessing enzyme activity at different pH levels to analyze data and make predictions.
This document is a worksheet on Newton's laws of motion. It contains questions and explanations about Newton's three laws: 1) An object at rest stays at rest and an object in motion stays in motion unless acted upon by an unbalanced force. 2) The acceleration of an object as produced by a net force is directly proportional to the magnitude of the net force, in the same direction as the net force, and inversely proportional to the mass of the object. 3) For every action, there is an equal and opposite reaction. The worksheet also covers concepts like inertia, mass, acceleration, friction, gravity, and their relationships as explained by Newton's laws.
This document contains a chapter test on forces and the laws of motion from a Holt Physics textbook. It includes 25 multiple choice and short answer questions testing concepts such as forces, inertia, Newton's laws of motion, weight, mass, and friction. It also provides the answers and solutions to sample word problems applying these physics principles. The test is meant to assess a student's understanding of the key topics covered in the chapter.
This document outlines the table of contents for a physics textbook, covering topics from motion and forces to electromagnetism, thermodynamics, waves, optics, and atomic and subatomic physics. Key chapters include motion in one and two dimensions, forces and laws of motion, work and energy, momentum and collisions, circular motion and gravitation, electricity and magnetism, circuits, and atomic and subatomic physics.
This document summarizes Newton's laws of motion and the different types of forces. It introduces Newton's three laws, including inertia, action-reaction pairs, and F=ma. Forces discussed include normal forces, friction, tension, and gravitational forces. It provides examples of applying free body diagrams and Newton's second law to solve mechanics problems. Key concepts are forces and Newton's laws, types of contact and other forces, and using physics equations to analyze motion.
Remote Sensing and Computational, Evolutionary, Supercomputing, and Intellige...University of Maribor
Slides from talk:
Aleš Zamuda: Remote Sensing and Computational, Evolutionary, Supercomputing, and Intelligent Systems.
11th International Conference on Electrical, Electronics and Computer Engineering (IcETRAN), Niš, 3-6 June 2024
Inter-Society Networking Panel GRSS/MTT-S/CIS Panel Session: Promoting Connection and Cooperation
https://www.etran.rs/2024/en/home-english/
BREEDING METHODS FOR DISEASE RESISTANCE.pptxRASHMI M G
Plant breeding for disease resistance is a strategy to reduce crop losses caused by disease. Plants have an innate immune system that allows them to recognize pathogens and provide resistance. However, breeding for long-lasting resistance often involves combining multiple resistance genes
Comparing Evolved Extractive Text Summary Scores of Bidirectional Encoder Rep...University of Maribor
Slides from:
11th International Conference on Electrical, Electronics and Computer Engineering (IcETRAN), Niš, 3-6 June 2024
Track: Artificial Intelligence
https://www.etran.rs/2024/en/home-english/
Or: Beyond linear.
Abstract: Equivariant neural networks are neural networks that incorporate symmetries. The nonlinear activation functions in these networks result in interesting nonlinear equivariant maps between simple representations, and motivate the key player of this talk: piecewise linear representation theory.
Disclaimer: No one is perfect, so please mind that there might be mistakes and typos.
dtubbenhauer@gmail.com
Corrected slides: dtubbenhauer.com/talks.html
hematic appreciation test is a psychological assessment tool used to measure an individual's appreciation and understanding of specific themes or topics. This test helps to evaluate an individual's ability to connect different ideas and concepts within a given theme, as well as their overall comprehension and interpretation skills. The results of the test can provide valuable insights into an individual's cognitive abilities, creativity, and critical thinking skills
The debris of the ‘last major merger’ is dynamically youngSérgio Sacani
The Milky Way’s (MW) inner stellar halo contains an [Fe/H]-rich component with highly eccentric orbits, often referred to as the
‘last major merger.’ Hypotheses for the origin of this component include Gaia-Sausage/Enceladus (GSE), where the progenitor
collided with the MW proto-disc 8–11 Gyr ago, and the Virgo Radial Merger (VRM), where the progenitor collided with the
MW disc within the last 3 Gyr. These two scenarios make different predictions about observable structure in local phase space,
because the morphology of debris depends on how long it has had to phase mix. The recently identified phase-space folds in Gaia
DR3 have positive caustic velocities, making them fundamentally different than the phase-mixed chevrons found in simulations
at late times. Roughly 20 per cent of the stars in the prograde local stellar halo are associated with the observed caustics. Based
on a simple phase-mixing model, the observed number of caustics are consistent with a merger that occurred 1–2 Gyr ago.
We also compare the observed phase-space distribution to FIRE-2 Latte simulations of GSE-like mergers, using a quantitative
measurement of phase mixing (2D causticality). The observed local phase-space distribution best matches the simulated data
1–2 Gyr after collision, and certainly not later than 3 Gyr. This is further evidence that the progenitor of the ‘last major merger’
did not collide with the MW proto-disc at early times, as is thought for the GSE, but instead collided with the MW disc within
the last few Gyr, consistent with the body of work surrounding the VRM.
Deep Behavioral Phenotyping in Systems Neuroscience for Functional Atlasing a...Ana Luísa Pinho
Functional Magnetic Resonance Imaging (fMRI) provides means to characterize brain activations in response to behavior. However, cognitive neuroscience has been limited to group-level effects referring to the performance of specific tasks. To obtain the functional profile of elementary cognitive mechanisms, the combination of brain responses to many tasks is required. Yet, to date, both structural atlases and parcellation-based activations do not fully account for cognitive function and still present several limitations. Further, they do not adapt overall to individual characteristics. In this talk, I will give an account of deep-behavioral phenotyping strategies, namely data-driven methods in large task-fMRI datasets, to optimize functional brain-data collection and improve inference of effects-of-interest related to mental processes. Key to this approach is the employment of fast multi-functional paradigms rich on features that can be well parametrized and, consequently, facilitate the creation of psycho-physiological constructs to be modelled with imaging data. Particular emphasis will be given to music stimuli when studying high-order cognitive mechanisms, due to their ecological nature and quality to enable complex behavior compounded by discrete entities. I will also discuss how deep-behavioral phenotyping and individualized models applied to neuroimaging data can better account for the subject-specific organization of domain-general cognitive systems in the human brain. Finally, the accumulation of functional brain signatures brings the possibility to clarify relationships among tasks and create a univocal link between brain systems and mental functions through: (1) the development of ontologies proposing an organization of cognitive processes; and (2) brain-network taxonomies describing functional specialization. To this end, tools to improve commensurability in cognitive science are necessary, such as public repositories, ontology-based platforms and automated meta-analysis tools. I will thus discuss some brain-atlasing resources currently under development, and their applicability in cognitive as well as clinical neuroscience.
The use of Nauplii and metanauplii artemia in aquaculture (brine shrimp).pptxMAGOTI ERNEST
Although Artemia has been known to man for centuries, its use as a food for the culture of larval organisms apparently began only in the 1930s, when several investigators found that it made an excellent food for newly hatched fish larvae (Litvinenko et al., 2023). As aquaculture developed in the 1960s and ‘70s, the use of Artemia also became more widespread, due both to its convenience and to its nutritional value for larval organisms (Arenas-Pardo et al., 2024). The fact that Artemia dormant cysts can be stored for long periods in cans, and then used as an off-the-shelf food requiring only 24 h of incubation makes them the most convenient, least labor-intensive, live food available for aquaculture (Sorgeloos & Roubach, 2021). The nutritional value of Artemia, especially for marine organisms, is not constant, but varies both geographically and temporally. During the last decade, however, both the causes of Artemia nutritional variability and methods to improve poorquality Artemia have been identified (Loufi et al., 2024).
Brine shrimp (Artemia spp.) are used in marine aquaculture worldwide. Annually, more than 2,000 metric tons of dry cysts are used for cultivation of fish, crustacean, and shellfish larva. Brine shrimp are important to aquaculture because newly hatched brine shrimp nauplii (larvae) provide a food source for many fish fry (Mozanzadeh et al., 2021). Culture and harvesting of brine shrimp eggs represents another aspect of the aquaculture industry. Nauplii and metanauplii of Artemia, commonly known as brine shrimp, play a crucial role in aquaculture due to their nutritional value and suitability as live feed for many aquatic species, particularly in larval stages (Sorgeloos & Roubach, 2021).
What is greenhouse gasses and how many gasses are there to affect the Earth.moosaasad1975
What are greenhouse gasses how they affect the earth and its environment what is the future of the environment and earth how the weather and the climate effects.
Phenomics assisted breeding in crop improvementIshaGoswami9
As the population is increasing and will reach about 9 billion upto 2050. Also due to climate change, it is difficult to meet the food requirement of such a large population. Facing the challenges presented by resource shortages, climate
change, and increasing global population, crop yield and quality need to be improved in a sustainable way over the coming decades. Genetic improvement by breeding is the best way to increase crop productivity. With the rapid progression of functional
genomics, an increasing number of crop genomes have been sequenced and dozens of genes influencing key agronomic traits have been identified. However, current genome sequence information has not been adequately exploited for understanding
the complex characteristics of multiple gene, owing to a lack of crop phenotypic data. Efficient, automatic, and accurate technologies and platforms that can capture phenotypic data that can
be linked to genomics information for crop improvement at all growth stages have become as important as genotyping. Thus,
high-throughput phenotyping has become the major bottleneck restricting crop breeding. Plant phenomics has been defined as the high-throughput, accurate acquisition and analysis of multi-dimensional phenotypes
during crop growing stages at the organism level, including the cell, tissue, organ, individual plant, plot, and field levels. With the rapid development of novel sensors, imaging technology,
and analysis methods, numerous infrastructure platforms have been developed for phenotyping.
1. Key Term
force
Force
You exert a force on a ball when you throw or kick the ball, and you exert a
force on a chair when you sit in the chair. Forces describe the interactions
between an object and its environment.
Forces can cause accelerations.
In many situations, a force exerted on an object can change the object’s
velocity with respect to time. Some examples of these situations are shown
in Figure 1.1. A force can cause a stationary object to move, as when you
throw a ball. Force also causes moving objects to stop, as when you catch a
ball. A force can also cause a moving object to change direction, such as
when a baseball collides with a bat and flies off in another direction.
Notice that in each of these cases, the force is responsible for a change in
velocity with respect to time—an acceleration.
The SI unit of force is the newton.
The SI unit of force is the newton, named after Sir Isaac Newton (1642–
1727), whose work contributed much to the modern understanding of
force and motion. The newton (N) is defined as the amount of force that,
when acting on a 1 kg mass, produces an acceleration of 1 m/s2.
Therefore, 1 N = 1 kg × 1 m/s2.
The weight of an object is a measure of the magnitude of the gravita-
tional force exerted on the object. It is the result of the interaction of an
Changes in Motion
Objectives
Describe how force affects the
motion of an object.
Interpret and construct
free-body diagrams.
force an action exerted on an object
that may change the object’s state of
rest or motion
Three Ways That Forces Change Motion Force can cause objects to
(a) start moving, (b) stop moving, and/or (c) change direction.
FIGURE 1.1
(b)
(a) (c)
Chapter 4
118
SECTION 1
Untitled-310 118 5/6/2011 12:01:56 PM
Differentiated Instruction
Below Level
Remind students that photographs, such as
those on this page, do not actually show
objects “experiencing force.” This is because
forces cause changes in velocity with respect
to time or direction. Challenge students to
explain what they would need to see in each
photograph if it was a video that showed the
effect of forces.
Preview Vocabulary
Academic Vocabulary In common
usage, the words pressure and force
sometimes are used interchangeably.
In physics, these words are distinctive.
Force is any effect or power that can
change the speed or direction of an
object in motion. Pressure is used only
to define the magnitude of a unit of
force exerted on a unit area. So, the
magnitude of pressure in physics
depends in part on the magnitude of
the force involved.
Teaching Tip
Now that students have studied motion
as complex as projectile motion, explore
their understanding of force. Ask them
what mechanism causes motion and
why some objects accelerate at higher
rates than others do. Point out that
force is attributed to any mechanism
that causes or may cause a change in an
object’s velocity with respect to time.
FIGURE 1.1 Point out to students that
the ball is experiencing force in all three
pictures.
Ask How can you tell that the ball
experiences at least one force in each
picture?
Answer: by changes in the ball’s speed
or direction
Plan and Prepare
Teach
TEACH FROM VISUALS
118 Chapter 4
SECTION 1
2. object’s mass with the gravitational field of another object, such as Earth.
As shown in Figure 1.2, many of the terms and units you use every day to
talk about weight are really units of force that can be converted to new-
tons. For example, a 1
_
4
lb stick of margarine has a weight equivalent to a
force of about 1 N, as shown in the following conversions:
1 lb = 4.448 N
1 N = 0.225 lb
Forces can act through contact or at a distance.
If you pull on a spring, the spring stretches. If you pull on a wagon, the
wagon moves. When a football is caught, its motion is stopped. These
pushes and pulls are examples of contact forces, which are so named
because they result from physical contact between two objects. Contact
forces are usually easy to identify when you analyze a situation.
Another class of forces—called field forces—does not involve physical
contact between two objects. One example of this kind of force is gravita-
tional force. Whenever an object falls to Earth, the object is accelerated
by Earth’s gravity. In other words, Earth exerts a force on the object even
when Earth is not in immediate physical contact with the object.
Another common example of a field force is the attraction or repulsion
between electric charges. You can observe this force by rubbing a balloon
against your hair and then observing how little pieces of paper appear to
jump up and cling to the balloon’s surface, as shown in Figure 1.3. The
paper is pulled by the balloon’s electric field.
The theory of fields was developed as a tool to explain how objects
could exert force on each other without touching. According to this
theory, masses create gravitational fields in the space around them.
An object falls to Earth because of the interaction between the object’s
mass and Earth’s gravitational field. Similarly, charged objects create
electromagnetic fields.
The distinction between contact forces and field forces is useful when
dealing with forces that we observe at the macroscopic level. (Macroscopic
refers to the realm of phenomena that are visible to the naked eye.) As we
will see later, all macroscopic contact forces are actually due to microscopic
field forces. For instance, contact forces in a collision are due to electric
fields between atoms and molecules. In fact, every force can be categorized
as one of four fundamental field forces.
Did YOU Know?
The symbol for the pound, lb, comes
from libra, the Latin word for “pound,”
a unit of measure that has been used
since medieval times to measure
weight.
Electric Force The electric field
around the rubbed balloon exerts an
attractive electric force on the pieces
of paper.
FIGURE 1.3
FIGURE 1.2
UNITS OF MASS, ACCELERATION, AND FORCE
System Mass Acceleration Force
SI kg m/s2 N = kg•m/s2
cgs g cm/s2 dyne = g•cm/s2
Avoirdupois slug ft/s2 lb = slug•ft/s2
Forces and the Laws of Motion 119
Untitled-310 119 5/6/2011 12:01:58 PM
FIGURE 1.3 Tell students that
both contact and field forces are
demonstrated in this picture.
Ask Identify the contact and field force
examples in the picture.
Answer: contact forces: the figure
supporting the pieces of paper, a person
supporting the balloon;
field forces: gravitational force pulling
down on the paper and balloon, electric
force pulling up on the paper
TEACH FROM VISUALS
English Learners
Write the prefixes macro- and micro- on the
board or overhead projector. Explain that the
prefix macro- refers to something large, while
the prefix micro- refers to something small.
Challenge students to come up with a definition
for words such as macroeconomics, microbe
macrobiology, microwave, and micrometer.
Allow students to use a dictionary to confirm
their definitions.
Forces and the Laws of Motion 119
3. PHYSICS
Spec. Number PH 99 PE C04-001-006-A
Boston Graphics, Inc.
617.523.1333
Force Diagrams
When you push a toy car, it accelerates. If you push the car harder, the
acceleration will be greater. In other words, the acceleration of the car
depends on the force’s magnitude. The direction in which the car moves
depends on the direction of the force. For example, if you push the toy car
from the front, the car will move in a different direction than if you push it
from behind.
Force is a vector.
Because the effect of a force depends on both magnitude and direction,
force is a vector quantity. Diagrams that show force vectors as arrows,
such as Figure 1.4(a), are called force diagrams. In this book, the arrows
used to represent forces are blue. The tail of an arrow is attached to the
object on which the force is acting. A force vector points in the direction
of the force, and its length is proportional to the magnitude of the force.
At this point, we will disregard the size and shape of objects and assume
that all forces act at the center of an object. In force diagrams, all forces are
drawn as if they act at that point, no matter where the force is applied.
A free-body diagram helps analyze a situation.
After engineers analyzing a test-car crash have identified all of the forces
involved, they isolate the car from the other objects in its environment.
One of their goals is to determine which forces affect the car and its
passengers. Figure 1.4(b) is a free-body diagram. This diagram represents
the same collision that the force diagram (a) does but shows only the car
and the forces acting on the car. The forces exerted by the car on other
objects are not included in the free-body diagram because they do not
affect the motion of the car.
A free-body diagram is used to analyze only the forces affecting the
motion of a single object. Free-body diagrams are constructed and
analyzed just like other vector diagrams. In Sample Problem A, you will
learn to draw free-body diagrams for some situations described in this
book. Later, you will learn to use free-body diagrams to find component
and resultant forces.
FORCE AND CHANGES
IN MOTION
Use a toy car and a book to
model a car colliding with a
brick wall. Observe the motion
of the car before and after the
crash. Identify as many chang-
es in its motion as you can,
such as changes in speed or
direction. Make a list of all of
the changes, and try to identify
the forces that caused them.
Make a force diagram of the
collision.
MATERIALS
1 toy car
•
1 book
•
Force Diagrams Versus Free-body
Diagrams (a) In a force diagram, vector
arrows represent all the forces acting in a
situation. (b) A free-body diagram shows only
the forces acting on the object of interest—in
this case, the car.
FIGURE 1.4
(b)
(a)
Chapter 4
120
Untitled-310 120 5/6/2011 12:02:00 PM
Differentiated Instruction
Pre-AP
Explain to students that forces acting on a
body at different points can produce transla-
tional movement of the body without
rotation; rotation without translational
movement; or translational movement and
rotation together, depending on exactly where
the forces act on the body. Discuss examples
of each situation. Then explain that the
examples in this chapter are limited to
translational movement without rotation,
so the sum of forces is all that is required.
For this reason, the forces can be drawn as
if they act on the body at a common point.
The concept of torque is discussed in the
chapter “Circular Motion and Gravitation.”
Rotational equilibrium and dynamics are
covered in the Take It Further feature
“Rotational Dynamics.”
Teacher’s Notes
If the toy car is rolled an appreciable
distance before the collision, students
may observe the car slowing down
because of friction. Give students a brief
explanation of friction.
Teach continued
QuickLab
120 Chapter 4
5. PHYSICS
Spec. Number PH 99 PE C04-001-006-A
Boston Graphics, Inc.
617.523.1333
Reviewing Main Ideas
1. List three examples of each of the following:
a. a force causing an object to start moving
b. a force causing an object to stop moving
c. a force causing an object to change its direction of motion
2. Give two examples of field forces described in this section and two ex-
amples of contact forces you observe in everyday life. Explain why you
think that these are forces.
3. What is the SI unit of force? What is this unit equivalent to in terms of
fundamental units?
4. Why is force a vector quantity?
5. Draw a free-body diagram of a football being kicked. Assume that the
only forces acting on the ball are the force due to gravity and the force
exerted by the kicker.
Interpreting Graphics
6. Study the force diagram on the right.
Redraw the diagram, and label each
vector arrow with a description of the
force. In each description, include
the object exerting the force and the
object on which the force is acting.
Drawing Free-Body Diagrams (continued)
1. A truck pulls a trailer on a flat stretch of road. The forces acting on the trailer are
the force due to gravity (250 000 N downward), the force exerted by the road
(250 000 N upward), and the force exerted by the cable connecting the trailer to
the truck (20 000 N to the right). The forces acting on the truck are the force due to
gravity (80 000 N downward), the force exerted by the road (80 000 N upward), the
force exerted by the cable (20 000 N to the left), and the force causing the truck to
move forward (26 400 N to the right).
a. Draw and label a free-body diagram of the trailer.
b. Draw and label a free-body diagram of the truck.
2. A physics book is at rest on a desk. Gravitational force pulls the book down.
The desk exerts an upward force on the book that is equal in magnitude to the
gravitational force. Draw a free-body diagram of the book.
Chapter 4
122
SECTION 1 FORMATIVE ASSESSMENT
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Answers to Section Assessment
1. Answers will vary.
2. gravity and electric force, answers will vary;
because they can cause a change in motion
3. the newton; 1 N = 1 kg•1 m/s2
4. because force has both magnitude and
direction
5. Fg
points down, and Fkicker
points in the
direction of the kick.
6. Each arrow should have a label identifying
the object exerting the force and the
object acted on by the force.
Answers
Practice A
1. Each diagram should include all
forces acting on the object, pointing
in the correct directions and with
the lengths roughly proportional to
the magnitudes of the forces. Be sure
each vector is labeled.
2. Diagrams should include a downward
gravitational force and an upward
force of the desk on the book; both
vectors should have the same length
and should be labeled.
Assess Use the Formative Assessment
on this page to evaluate student
mastery of the section.
Reteach For students who need
additional instruction, download the
Section Study Guide.
Response to Intervention To reassess
students’ mastery, use the Section Quiz,
available to print or to take directly
online at HMDScience.com.
Teach continued
Assess and Reteach
122 Chapter 4