2. Warm-upMon. 3/19/07 5 min to perfect your lab in silence… No Talking. You don’t talk, you get time to work. You talk, You get a fat zero on the lab.

3. Newton’s Third Law Action-Reaction Chapter 4

4. Interactions What is an interaction? –Exchange of actions between two objects –Requires a FORCE from both objects

5. Force as Interaction Let’s look at the binder-clips and rubber bands: 1.Try to open your binder-clip, using only one hand on one side of the clip 2.Press it on the desk… is the desk pushing? 3.Now, working with a partner open the binder clip with only one hand on one side (each)

6. Rubber Band 1.With a partner, stretch the rubber band. 2.Try to stretch the rubber band using just one hand. 3.Hook it on your desk… 4.…is the desk pulling? Non-living objects can push and pull!

7. Newton’s Third Law When object A exerts a force on a object B, then object B object exerts an EQUAL and OPPOSITE force on object A. For every action, there is ALWAYS an equal and opposite reaction

8. Example Time

9. The book has a weight of 10N What force is the book exerting on the table? What force is the table exerting on the book? Table on Book: 10N Book on Table: 10N

10. Action-Reaction Action = Book’s 10N Force down on the table Reaction = Table’s 10N Force up on the book Magnitude = Same Direction = Opposite

11. The man is pushing on the wall with a force of 25N to the right. Action Force: ? Reaction Force: ?

12. Action-Reaction We call these Action-Reaction forces… FORCE PAIRS –Forces always occur in pairs –Equal magnitude and opposite direction!

13. Let’s look at a balloon… If I blow it up, then let it go… –What is the interaction? Force exchange between balloon and escaping air –What is the action? Balloon pushing DOWN on air with some Force –What is the reaction? Air pushing UP on balloon with an EQUAL and OPPOSITE Force!!!

14. ACTION: Balloon pushes on air with a Force REACTION: Air pushes back on balloon with an EQUAL and OPPOSITE Force

15. Think About It… What is the force pair that allows a bird to fly? –What is the interaction –What is the Action Force? –What is the Reaction Force?

16. Interaction: Between Wing and Air Action: Wing pushes DOWN on air with some Force Reaction: Air pushes UP on wing with an EQUAL Force

17. What is the interaction in this picture? What is the Action? What is the Reaction?

18. Foot exerts a force on the ball Ball exerts an EQUAL and OPPOSITE force on the foot

19. Let’s look at some car crashes… Think of the INTERACTIONS in these accidents!!!! Just a sec….

20. Car vs. Wall A car hits a wall with a force of 500N… What is the interaction –Exchange of forces between car & wall What is the Force Pair? –Action Car exerts a force on the wall –Reaction Wall exerts an equal and opposite force on the car Draw this in your notebook!

21. Somebody show me what you got on the board…

22. Warm-Down… Newton’s Third Law –For every Action there is an EQUAL and OPPOSITE R_____________ Forces happen in P_______ –An interaction includes an A_____ F_______ and a R_______ F____ eaction airs ctionorce eaction

23. “Dark and Stormy Night” Activity…