FORCE AND MOTION

What do you know about force and motion?

Georgia Performance Standards

S4P3: Students will demonstrate the relationship between the application of a force and the resulting change in position and motion on an object.

a. Identify simple machinesb. Using different size objects, observe how force affects

speed and motion.c. Explain what happens to the speed or direction of an

object when a greater force than the initial one is applied.

d. Demonstrate the effect of a gravitational force on the motion of an object.

ESSENTIAL QUESTIONS

• How can force be used to make objects move, change direction, or stop?

• How is the motion of an object related to the size of the object and the amount of force that is applied to the object?

• What is gravity and how does it affect things on the earth?

• How do simple machines make work easier for people?

Motion

• The motion of an object can be described by its speed and direction. Speed and direction together determine an objects velocity.

POSITION

• Position is an object’s location.

• How would you describe your location?

• What would happen to your position if you moved?

MOTION

• Motion is the change in an object’s location as compared to the object around it.

• If you move, your location changes when you compare it to the objects around you.

Motion

• An object can appear to be moving when compared to certain objects but not to others.

• Think about when you and a friend are riding in a car. Compared to each other and the car, you and your friend are not moving. However, when you are compared to objects outside the car, you and your friend are moving.

Earth is Moving

• Even when you are standing still, the Earth is still moving.

SPEED

• Speed is a measure of the distance an object travels in a certain amount of time.

• You can find the speed of an object if you know the distance the object traveled and how long it took to travel that distance.

• Divide the distance by the time to find the SPEED.

SPEED

• If a car travels 100 miles in 2 hours, its SPEED is 50 miles per hour (MPH).

• 100 (the amount of miles) divided by 2 (the time) equals 50.

• This gives you the speed of the car.

EVERY MOTION HAS A SPEED

• Some objects move very slowly.

• Some objects move very quickly.

Speed

• Glaciers move so slowly that they only move downhill a few meters in a year.

Speed

• The wings of a hummingbird move up and down so fast that they are just a blur.

DIRECTION

• Each motion has a direction as well as a speed.

• DIRECTION tells you which way an object is moving.

• You can describe direction using words such as EAST, WEST, NORTH, SOUTH, RIGHT, LEFT, UP, or DOWN.

VELOCITY

• Speed and direction together determine the VELOCITY.

• Velocity is the measure of speed in a certain direction.

FORCES OF MOTION

• A force is a push or a pull.

• A push is a force that moves objects AWAY.

• A pull is a force that moves an object closer.

FORCE

• A force can change the motion of an object.

• A force can start an object moving, change the direction or speed of the object, or stop the object from moving.

• To change the speed or direction of an object, you must change the force.

FRICTION

• The force that stops some objects from moving when you stop pushing them is called FRICTION.

• FRICTION is a force that slows or stops motion between two surfaces that are touching.

• Friction exists between any two forces that are touching. There is more friction between things that are rough and there is between things that are smooth.

FRICTION

• FRICTION can be useful. Without friction, we would slip and slide on every surface.

• Without friction, your pencil would slide between your fingers and you would not be able to write.

GRAVITY

• GRAVITY is a force that pulls objects towards each other.

• Earth’s gravity is what pulls skydivers towards the ground when they jump out of an airplane.

• Gravity is what keeps your book on your desk and makes the rain fall from the clouds.

SIMPLE MACHINES

• SIMPLE MACHINES help people do work by changing a force. A machine is any tool that makes work easier.

• Types of simple machines are an INCLINED PLANE, WEDGE, SCREW, LEVER, WHEEL AND AXLE, and a PULLEY.

INCLINED PLANE

• An inclined plane is a simple machine made up of a slanted surface.

• Ramps are examples of inclined planes.

• Inclined planes make it easier

to raise an object.

WEDGE

• Is a simple machine made up of two inclined planes. It is V-shaped. It changes a downward force to an outward force.

• This simple machine helps to cut or split apart objects.

SCREW

• This is a simple machine made up of an inclined plane wrapped around a column.

• It changes a weak circular force to a strong downward force.

LEVER

• This is a simple machine that is made up of a stiff bar that moves freely around a fixed point.

• Examples of levers are see-saws and can-openers.

WHEEL and AXLE

• This is a simple machine made up of two cylinders that turn on the same axis.

• The outer cylinder is called the wheel. The inner cylinder, which is smaller, is called the axle.

• Examples of wheels and axles are car steering wheels and doorknobs.

PULLEY

• This machine is made up of a rope fitted around the rim of a fixed wheel.

• Pulleys are used to raise and lower elevators, to move clothes lines back and forth, and to lift a flag up a flagpole.

COMPOUND MACHINES

• Many of the things that you use every day are made of two or more simple machines.

• A compound machine is when two or more simple machines are put together to help you do work.

COMPOUND MACHINE

• Scissors are made of two levers with a fulcrum in the middle, The cutting blades of the scissors are wedges.

COMPOUND MACHINEA bicycle uses many simple machines. The

pedals are levers that supply force to the sprocket. The sprocket is a wheel and axle that uses gears to move the chain.

ESSENTIAL QUESTIONS

• How can force be used to make objects move, change direction, or stop?

• How is the motion of an object related to the size of the object and the amount of force that is applied to the object?

• What is gravity and how does it affect things on the earth?

• How do simple machines make work easier for people?