E s s e n t i a l Q u e s t i o n s : Wh a t i s a• When you jump up in c e ? f o r the air, what pulls you back down W Earth? t to h a e f f e c t• What pulls e magnet together oro r c it e d o a s a f pushes apart?• The answer is…. h a v e o n a n o b j e c t ?
A FORCE is a push or pull that causes a change in motion.• Nothing can change position, speed, or direction unless a force acts on it.• A book doesn’t just fall off of a table by itself. A force has to push it! Forces can affect motion in several ways: → They can make objects start moving → They can make objects move faster → They can make objects move slower → They can make objects stop moving → They can make objects change direction
Essential Questions: What happens when twounequal forces push an object in the same direction? What happens when two unequal forces push and object in opposite directions?
E s s e n t i a l Q u e s t i o n s : Wh a t a r e s o m e•Friction- ise force that works against motion e s t y p a s o f f o r c • can makefthingsi slow down or o n or it ( r c t i stop, , can keep things from moving at all • greater between a v surfaces than between g r rough i t y , msmooth one e t i c a g n f o r c e ) •Ice skaters glide along? ice because there is the little friction between the blades and the ice.
E s s e n t i a l Q u e s t i o n s : Wh a t a r e s o m et y p e s o f f o r c e s Gravity f r i c t ie o n , ( i s t h u n i g r a v ia t y , v e r s lm aa t g t n r e at c i t c i o f n o r c e ) b e t w e e n? a n y t w o o b j e c t s w i t h m a s s .
E s s e n t i a lQ u e s t i o n s : Wh a t a r e s o m e t y p e s o f f o r c e s Magnetic ( f r i c that i o n iron is Force- anything t attracts , considered g r a That’s why y , clips are magnetic. v i t paper attracted to a magnet. Paper clips contain iron. The m a g called the magnetic force. force of a magnet is n e t i c A magnet is afpiece of metal that pulls? attracts o r c e ) or things which have iron or steel in them. The most common magnets are in the shape of a bar or horseshoe. The magnet is surrounded by a force field which attracts iron, especially at the poles.
M a g n e t s a r es u r r o u n d e d b y a f o r c e f i e l d w h i c ha t t r a c t s i r o n ,e s p e c i a l l y a t t h e
Let’s ReviewWhich of the following is an example of trying to increase the friction?A. Squirting oil in hingesB. Spreading grit on icy roadsC. Waxing the underneath of skis
Mr. Gates mops the gymnasium floor every day.When he finishes mopping, he puts up the signshown below. The effect of which force is weakenedwhen the floor is wet?A. frictionB. gravitationC. inertiaD. magnetism
Let’s Review N S S N What is happening between these two magnets?• A.) The magnets pull toward each other because like poles attract.• B.) The magnets push away from each other because like poles attract.• C.) The magnets pull toward each other because like poles repel.• D.) The magnets push away from each other because like poles repel.
Let’s ReviewOn which surface will a toy car travel the farthest?A. IceB. WoodC. Carpet
Let’s ReviewWhich of the following is NOT a type of force?A. magneticB. frictionC. motionD. gravity
Characteristics of Motion• The motion of an object can be described by its: • Position • Direction • Speed • Velocity• Position, direction, speed, & velocity can be changed by forces that act on the object.
Position• Position is the location of an object 2 feet• The dog is 2 feet away from the tree. This picture shows the position of each object: the dog and the tree.
Direction• Motion can also be described using directions such as north, south, east, & west. Direction of an object depends on the direction of the force. It can be measured with a compass.• The bird flew up, the car turned left, the rabbit ran toward the gate, the dog ran away from the house• Objects can also move toward and away.
Speed• Position and direction are helpful in describing motion. Yet motion also occurs over time. • For example- You threw a football 20 meters. But did the football go 20 meters in 2 minutes? 2 seconds?• Speed is the measurement of distance over time.• You can use a stopwatch to measure speed
Velocity• Velocity is the object’s speed BUT includes direction• Remember, DIRECTION includes north, south, east and west- following the points of a compass. • For example- the football that was thrown 20 meters in 2 seconds is traveling 10 meters per second (20/2 = 10). You MUST include direction for velocity. So your answer might really be 10 meters per second west! States the direction the ball traveled
Measuring Motion• Scientists use many tools to measure motion: • Commonly used to measure direction is the compass. • A meterstick is commonly used to measure distance between one position and another. • A stopwatch is used to measure time
Let’s Review• Which of the following is the BEST description of the position of the eraser? • A.) The eraser is near the pencil • B.) The eraser is to the left of the pencil 4 cm • C.) The eraser is 4 cm away from the pencil • D.) The eraser is 4 cm to the left of the pencil
Let’s Review• What is the speed of a hockey puck that moves 45 meters in 5 seconds? • A.) 45 meters per second • B.) 17 meters per second • C.) 9 meters per second • D.) 5 meters per second
Let’s Review• What is velocity? • A.) speed and position • B.) speed and direction • C.) position and direction • D.) direction and time
Newton’s First Law of Motion“An object at rest tends to stay at rest and an object in motion tends to stay in motion unless acted upon by an unbalanced force.”
Newton’s First Law of Motion With no net force acting upon it, an object at rest tends to stay at rest, an object in motion tends to stay in motion. Both objects will continue with the same inertia keeping the same velocity.• A soccer ball doesn’t just roll across the field on its own. • It takes a force (such as a kick) to move the ball. • Once the ball moves, it doesn’t just move forever. Eventually it will stop. • Earth’s gravity and friction stop moving objects.
Newton’s Second Law of Motion The acceleration of an object depends on the mass of the object and the size of the force acting on it.Acceleration: a measurement of how quickly an object is changing speed.
NEWTON’S SECOND LAWThe more mass an object has, the harder it is to accelerate.The less mass an object has, the easier it is to accelerate.
Newton’s Third Law of Motion “For every action there is an equal and opposite reaction.”
Forces occur in pairs- for every action there is an = and opposite reaction.As the runner’s footpushes on thestarting block(action force), thestarting block isexerting a force onthe runner’s foot(reaction force).
Let’s ReviewA(n) __________ is a push or a pull.B) motionD) velocityF) AccelerationD) force
Let’s Review• Which of the following is not an acceleration?• A) stopping your bike at an intersection• B) slowing your bike ride so you can make it up a hill• C) riding your bike faster when you head down a hill• D) riding your bike straight down the street at a constant speed
Let’s Review Forces that cancel each other are called __________ forces.• A) neutral• B) balanced• C) inactivated• D) null
Let’s Review• Whenever one object exerts a force on another object, the second object ALWAYS exerts an equal force back on the first object. • A.) True • B.) False
Let’s Review• Forces always occur in ______________. • A.) Triplets • B.) Pairs • C.) by themselves • D.) either singly or in pairs
Let’s Review• Newtons first law of motion states that __________.• A) an object will remain at rest or keep moving with a constant velocity unless a force acts on it• B) acceleration is calculated by dividing the force exerted on an object by the mass of the object• C) when a force acts on an object, its acceleration is in the same direction as the force• D) when a force is applied on an object, there is an equal force applied by the object in the opposite direction
Let’s Review__________ is a force that resists motion between two surfaces.• A) Resistance• B) Inertia• C) Friction• D) Acceleration
Essential Question: Why do we need simple machines? What are the 6 simple machines?Work means that we are exerting force and moving something.The 6 simple machines make our work easier. We won’t have touse as much force with our simple machines.
The Wheel and Axle• Two or more wheels are connected by an axle• The wheel turns with or around the axle
Pulley• A pulley is a wheel with a rope running over it. The wheel has a groove, called a sheave, and it keeps the rope from slipping off the wheel.• Remember, since there is a wheel in a pulley there also has to be an axle!
Lever• There are two parts to a lever: • The Lever Arm: the arm that moves • Fulcrum: the support or balance that does NOT move
The Wedge• A wedge is a special kind of inclined plane made of two slopes, back to back.• Wedges can be used to move things apart.• Wedges can change the direction of the applied force.• A wedge is used to split, tighten, or secure a hold.• A wedge is usually a triangle shape with a sharp point.• If you apply force at one end, the wedge will go between something, in this case an ax splits a piece of wood.
The Inclined Plane• The inclined plane is a plane surface set at an angle, other than a right angle, against a horizontal surface. The inclined plane permits one to overcome a large resistance by applying a relatively small force through a longer distance than the load is to be raised. • A screw is a rod with an inclined plane wrapped around it. The spiraling inclined plane forms ridges which are called threads.
Let’s ReviewWhich of the following is NOT a simple machine?A.) inclined planeB.) wedgeC.) elevatorD.) screw
Let’s ReviewA fork is an example of a:A.) pulleyB.) wedgeC.) wheel and axleD.) lever
Let’s ReviewA saw, a knife, and a doorstop are all examples of what type of simple machine?A.) inclined planeB.) wedgeC.) pulleyD.) screw
Let’s ReviewA teeter totter on the playground is an example of what type of simple machine?A.) leverB.) wedgeC.) pulleyD.) inclined plane
Standards Covered• SC.C.1.2.1- The student understands that the motion of an object can be described and measured.• SC.C.1.2.2- The student knows that waves travel at different speeds through different materials.• SC.C.2.2.1- The student recognizes that forces of gravity, magnetism, and electricity operate simple machines.• SC.C.2.2.4- The student knows that the motion of an object is determined by the overall effect of all of the forces acting on the object.