1. Unit 4 Motion & Forces

2. 5. Laws of Motion

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

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

5. 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

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

7. If the object is moving
it will keep moving

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

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

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

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

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

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

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

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

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

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

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