1. Physical Science 2B.1.1 Specification “f”
Action – Reaction Forces:
Force Pairs

2. For every action, there is an equal, but opposite reaction.
For every push, there is a pull.
Equal in magnitude
Size [25 Newtons, 12.5 pounds, etc]
Numerical value
Opposite in direction
east vs. west
up vs. down.

3. Example Source: Physics, 5th Edition, Giancoli, Chapter 4
Example Source: Physics, 5th Edition, Giancoli, Chapter 4. Physics textbook used at BVW. Equal Magnitude, Opposite Direction!

4. Example Source: Physics, 5th Edition, Giancoli, Chapter 4
Example Source: Physics, 5th Edition, Giancoli, Chapter 4. Physics textbook used at BVW. Equal Magnitude, Opposite Direction!

5. Example Source: Physics, 5th Edition, Giancoli, Chapter 4
Example Source: Physics, 5th Edition, Giancoli, Chapter 4. Physics textbook used at BVW. Equal Magnitude, Opposite Direction! GP = Ground exerting force on Person PG = Person exerting force on Ground

6. Example Source: Physics, 5th Edition, Giancoli, Chapter 4
Example Source: Physics, 5th Edition, Giancoli, Chapter 4. Physics textbook used at BVW. Equal Magnitude, Opposite Direction!

7. Example Source: Physics, 5th Edition, Giancoli, Chapter 4
Example Source: Physics, 5th Edition, Giancoli, Chapter 4. Physics textbook used at BVW. Equal Magnitude, Opposite Direction! G = Gravitational (Earth pulling down) N = Normal (surface pushing up)

8. Question: Source: Physics, 5th Edition, Giancoli, Chapter 4
Question: Source: Physics, 5th Edition, Giancoli, Chapter 4. Physics textbook used at BVW. Identify action-reaction force pairs for the following: The truck and Chris. The ground and Mary. The tires and Earth (vertical). The tires and Earth (horizontal).

9. Answers: Source: Physics, 5th Edition, Giancoli, Chapter 4
Answers: Source: Physics, 5th Edition, Giancoli, Chapter 4. Physics textbook used at BVW. The truck and Chris. Truck pushing up (normal force); Chris pushing down (gravitational force). Truck pushing Chris’s shoes to the right (direction of acceleration); Shoes pushing to the left. Shoes push Chris right, Chris pushes shoes left. The ground and Mary. Ground pushign up (normal); Mary pushing down (gravity). The tires and Earth (vertical). Ground pushing up; tires pushing down. The tires and Earth (horizontal). Ground pushing right (direction of acceleration); tires pushing ground to the left.

10. Questions: Source: Physics, 5th Edition, Giancoli, Chapter 4
Questions: Source: Physics, 5th Edition, Giancoli, Chapter 4. Physics textbook used at BVW. Assume the two buckets have equal masses, and thus have equal weights. Weight is mass acted upon by gravity. 1. What is the lower cord [rope] holding up? 2. What is the lower cord pulling down on? 3. What is pulling up on the lower cord? 4. What is pulling down in the lower cord? [two things] 5. What is holding up the lower bucket? 6. What is holding up the top bucket? 7. What is pulling down in the top bucket? [two things] 8. What is pulling down in the bottom bucket? [one thing] 9. Do the two cords have equal tensions? Explain.

11. Answers: Source: Physics, 5th Edition, Giancoli, Chapter 4
Answers: Source: Physics, 5th Edition, Giancoli, Chapter 4. Physics textbook used at BVW. Assume the two buckets have equal masses, and thus have equal weights. Weight is mass acted upon by gravity. 1. What is the lower cord [rope] holding up? Lower bucket. 2. What is the lower cord pulling down on? Top bucket. 3. What is pulling up on the lower cord? Top bucket. 4. What is pulling down in the lower cord? [two things] Lower bucket AND gravity (cord has mass!). 5. What is holding up the lower bucket? Lower cord. 6. What is holding up the top bucket? Top cord. 7. What is pulling down in the top bucket? [two things] Gravity AND the lower cord. 8. What is pulling down in the bottom bucket? [one thing] Gravity. 9. Do the two cords have equal tensions? No. Explain. Top cord is “holding up” both buckets. Lower cord is “holding up” the lower bucket.