1. Section 2.3 Forces act in pairs

2. Vocabulary Newton’s third law
_______________________________ states that every time one object exerts a force on another object, the second object exerts a force that is equal in size and opposite in direction back on the first object.

3. What does his 3rd law really say?
If you push on a wall you feel a force against your hand…the wall is pushing back on you with as much force as you apply to it.
If this wasn’t happening, your hand would accelerate through the wall!

4. Action and Reaction Pairs
The force that is exerted on an object and the force that the object exerts back are known together as an ___________________ force pair.
The jellyfish pushing on the water is the action force.
The water pushing back on the jellyfish is the reaction force.
action/reaction

5. Action and Reaction Pairs

6. Action and Reaction Pairs
Action force: the hammer hitting the stake.
Reaction force: the stake pushing up against the hammer.

7. Action and Reaction Pairs
The tires on a car push on the road.
The road pushes on the tires.

8. Action and Reaction Pairs
A rocket pushes out exhaust downward.
The exhaust pushes the rocket upward.

9. Action and Reaction Pairs vs. Balanced and Unbalanced Forces
Balanced forces act on a _________________________.
Action/reaction forces act on __________________________.
single object
different objects

10. Applying Newton’s 3 Laws
Newton’s 3rd Law
Newton’s 1st Law
Newton’s 2nd Law
Gravity
Friction
Contact
Acceleration
Action/Reaction Pair
The larger kangaroo does not have as much acceleration as a smaller kangaroo if they use the same force to jump.
The force of gravity will bring the kangaroo back to the ground.
A kangaroo applies an action force on the ground and the ground applies a reaction force.