This document provides an overview of key concepts from a chapter on forces and motion, including: 1) It defines types of motion, speed, velocity, and Newton's laws of motion, which describe how forces affect the motion of objects. 2) It explains different types of forces like gravity, magnetism, electricity, and friction and how they impact motion. 3) It introduces the concept of work and power, and describes how simple machines like levers, pulleys, and inclined planes can be used to make work easier to accomplish.

1. Chapter 13 Forces in Motion

2. You Will Discover: How motion is measured. How force affect motion, work, power. What Newton’s laws of motion are. How simple machines make work easier.

3. Chapter 13 Vocabulary Velocity: the speed and direction of an object’s motion Force: a push or pull that acts on an object Work: energy used when a force moves on an object Power: the rate at which work is done Equilibrium : the state in which the net force is zero Inertia: the tendency of an object to resist a change in motion Acceleration: the rate at which the velocity of an object changes over time. Machine: a device that changes the direction or the amount of effort needed to do work.

4. Lesson 1: How can you describe motion? Types of Motion Steady or Constant - the Earth has steady motion as it moves around the Sun. Variable - cars, trucks, and buses because they move in many directions and at many speeds. Periodic - a pendulum, swings back and forth Circular - wheels Vibrational - a rubber band when you pluck it

5. Examples of Motion Steady or Constant Periodic Variable Vibrational Circular

6. Speed Average Speed: describes how far an object moves during a certain amount of time. Average Speed = Distance Time The motion of an object cannot be measured by just looking at the object. Motion is always measured in relationship with some location called a point of reference. The speed at which a person is moving can vary according to which point of reference you use.

7. Speed Formula Point of Distance Time Speed Reference Train Car 10 m 5 s 10m = 2 m/s 5 s Signal 150 m 5 s 150m = 30 m/s Light 5 s

8. Velocity Speed and Velocity are not the same! Velocity describes the speed and the direction of an object’s motion. Example: the speed of the train might be described as 30 meters per second, but its velocity is 30 meters per second North.

9. Questions to Discuss What are five types of motion? Give an example for each one. What do you need to know to find an objects velocity? What is a point of reference? If you were riding a bicycle, is your motion constant, variable, or periodic? Explain.

10. Lesson 2 - What are forces? Pushes and Pulls A Force is a push or pull that acts on an object. When one object pushes or pulls another object, the first object is exerting a force on the second one. Forces can make a moving object speed up, slow down, or change direction. Forces have both magnitude and direction. Magnitude is measured in newtons (N). The direction of a force can be described by telling which way the force is acting.

11. Gravity Every object in the universe exerts a gravitational pull on every other object. An object’s weight is the amount of gravitational force between it and Earth. -This depends on the object’s mass and Earth’s mass.

12. Magnetism Magnetism is a force that pushes or pulls on other objects . Magnets will strongly pull on objects made of iron, cobalt, nickel, and gadolinium. The north and south poles of two magnets will push away from each other.

13. Electricity Electric forces act between objects that are electrically charged. Objects get electrically charged when they gain or lose electrons. All atoms have negative electrons and positive protons. If an object gains electrons , the object will be negatively charged. If an object loses electrons, it will be positively charged.

14. Electricity Electrons move from one object to another when: The objects are rubbed together. Objects that are electrically charged will exert forces on each other. Oppositely charged objects are attracted to each other. Objects with the same charge are repelled from each other.

15. Friction Friction is the force that results when two materials rub against each other. Friction acts to slow down the motion of an object or keep it from starting to move. Friction depends on the qualities of the object involved. The shape, speed, or texture of one object can affect the amount of friction.

16. Work Work is done when a force moves an object. To calculate work: Force x Distance = Work Work is measured in joules. 20 N x 2 m = 40 J 2 m 20 N 10 N x 2 m = 20 J 2 m 10 N 10 N x 1 m = 10 J 1 m 10 N Work Distance Force

17. Work If the force applied to an object, does not make the object move, then no work has been done. Work is only done when the object moves. Holding an object in place can require a force, but since the object doesn’t move no work is done.

18. Power Power is the rate at which work is done . The faster work is done, the power is increased. To calculate the amount of power: Work = Power Time

19. Questions to Discuss What are the causes of electrical and magnetic forces? How does friction affect movement? What are two examples of forces? What kind of force can make a paper clip cling to a comb? In what unit is work measured? In what unit is power measured?

20. Lesson 3 - What are Newton’s laws of motion? NET FORCES Different forces can act on an object at the same time. They may act in the same direction, different directions, and some may be stronger than others. The combination of all these forces is the NET FORCE! The net force determines whether the object start or stop moving or change direction.

21. Net Forces Equal forces working in opposite directions, balance those forces. The net force is zero . This is called equilibrium. A stationary object will remain motionless. A moving object in will continue to move at a constant speed in a straight line. Unbalanced forces acting on an object causes it to change motion.

22. Newton’s First Law Unless a net force acts on an object , the object will remain in constant motion. An object at rest stays at rest until a net force acts upon it. An object moving at a constant speed will continue to move in a straight line and at a constant speed.

23. Newton’s Second Law Acceleration is the rate at which the velocity of an object changes over time. The net forces acting on an object can change an object’s velocity by causing it to speed up, slow down, or change directions. The formula that describes the relationship between force, mass, and acceleration is: Force = Mass x Acceleration The stronger the force the more that object will accelerate.

24. Newton’s Third Law When one object exerts a force on a second object, the second object exerts a force on the first object. This is sometimes called the action-reaction law of motion. Action-reaction forces are always equal and opposite , and they occur in pairs .

25. Questions to Discuss What is the net force on an object? What does an object look like that is in equilibrium? What does Newton’s first law of motion state? The second law? The third law? How does force affect acceleration? Why do action-reaction forces always occur in pairs?

26. Lesson 4 - What are simple machines? Machines and Work: Work is done when a force causes an object to move. A machine is a device that changes the direction or the amount of force needed to do work . Machines do not reduce the amount of work that needs to be done , it just makes it easier . There are four types of simple machines: pulley, wheel and axle, lever, inclined plane

27. Pulley A pulley consists of a rope or cable that runs through a grooved wheel. *Examples: flag pole drapery rods

28. Wheel and Axle A wheel and axle is made up of a circular object and a shaft. *Examples: steering wheel door knob

29. Lever A lever is made up of a stiff bar that rotates around a fixed point called a fulcrum . *Examples: tongs clothes pins pliers

30. Inclined Planes An inclined plane consists of a flat surface with one end higher than the other. *Examples: screws, wedge, doorstop ramps,

31. Complex Machines A complex machine uses two or more simple machines put together . Many complex machines use electricity, gravity, burning fuel, human force, or magnetism to operate Examples: washing machine go cart car s ailboat

32. Questions to Discuss Why is a screw considered a simple machine? What is a complex machine? How is the movement of rolling a weight up an inclined plane different from climbing stairs? What is a machine? List the four simple machines. What is one example of each simple machine?