1. Newton’s 3rd Law
11/27/13

2. Newton Hat Trick Video

3. Newton’s 3rd Law
11/24/14
(AP)

4. Newton’s 3rd Law
12/2/14

5. Background Information Newton’s Law of Universal Gravitation
The Principia - Mathematical Principles of Natural Philosophy
Newton’s three laws of motion is the foundation for his Universal Law of Gravitation

6. Newton’s Laws Quick Summary
1st Law:
An object at rest stays at rest
An object in motion stays in motion with the same velocity, if no net force
2nd Law:
Accelerations are do to the net forces on an object (mass)
3rd Law:
Action and reaction pair of forces

7. Newton’s 3rd Law (recap)
Law III: To every action there is always an equal and opposite reaction: or the forces of two bodies on each other are always equal and are directed in opposite directions.
When one body exerts a force on a second body, the second body exerts an equal and opposite force on the first.
TWO objects and TWO forces
Forces always come in pairs

8. Newton’s 3rd Law TWO Forces and TWO objects (TWO different F.B.D.)
IF object A pushes/pulls on object B
THEN object B pushes/pulls on object A in the opposite direction
Object A push/pull – Action Force
Object B push/pull – Reaction Force

9. Newton’s 3rd Law Examples
The action force will be stated
Identify the reaction force
Draw the reaction force vector

10. Newton’s 3rd Law Examples
Flower pulls on hand

11. Newton’s 3rd Law Examples
Ball hits the bat

12. Newton’s 3rd Law Examples
The Earth pulls on the skydiver.
The skydiver pulls on the Earth.

13. Newton’s 3rd Law Examples
Draw a F.B.D. of both objects and identify the action force and reaction force.
Mr. Z. kicks a ball across to floor. What is the action force and reaction force?
Action Force: Mr. Z. kicking the ball.
Reaction Force: The ball pushing on Mr. Z.

14. Free Body Diagrams
Mr. Z.
Tennis Ball

15. Newton’s 3rd Law Examples
One last example …
This one is simple but a bit tricky!

16. Newton’s 3rd Law You (a student) sitting in a chair.
Identify all action-reaction pairs
Draw a free body diagram from each object
Question: How many objects are involved in this situation?
Three!
You (the student), chair and the Earth
Labeling the action-reaction pairs on the F.B.D.

17. Homework
Newton’s 3rd Law Practice
Due Tues. 11/25/14

18. Newton’s 3rd Law Examples
You (a student) sitting in a chair.
What are the action forces (two)?
1) The Earth pulling you down
2) You pushing on the chair
These are both ACTION forces!
What are the reaction forces?
1) You pulling on the Earth
2) The chair pushing on you

19. Free Body Diagrams

20. Homework
Newton’s 3rd Law Practice
Due Tues. 11/25/14