Unit 4 Motion & Forces

5. Laws of Motion

About 300 years ago, a scientist named Isaac Newton had some ideas about forces and motion

His ideas became known as Newton’s Law’s of Motion They are called laws because they correctly explain certain happenings around you

the object will keep its state of motion One of the Newton’s laws says that if all the forces acting on an object are balanced the object will keep its state of motion

In other words, if the object is at rest, or not moving it will stay at rest, or not move

If the object is moving it will keep moving

The state of motion will stay the same unless the forces become unbalanced by some other force

Suppose you see a soccer ball on the grass It is at rest

The force of the ground pushing up on it is balanced by the force of gravity pulling down on it

The soccer ball will keep its state of motion which in this case is no motion

Suppose you kick the ball You have unbalanced the forces with the force of your kick

The ball will be in motion The ball will stay in motion until some other force comes along

In this case, a force called friction will stop the ball after awhile

Another law of motion says that for every action there is an equal and opposite reaction

When a rocket is launched burning fuel makes hot gases come out of the bottom of the rocket

The rocket pushes on the gases and takes off moving away from Earth

The gases pushing the rocket is the action Reaction The rocket moving up is the reaction