Conceptual Physics Chapter 7 Newton's Third Law

A flash card set for Chapter 7 of Conceptual Physics by Hewitt
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Why do forces always occur in pairs?
A force is always part of a mutual action that involves another force.
Interaction
A mutual action between one thing and another.
Newton's third law
Whenever one object exerts a force on a second object, the second object exerts an equal and opposite force on the first object. More simply, to every action there is an equal and opposite reaction.
Action force
The force that is equal in strength but opposite in direction to a reaction force.
Reaction force
The force that is equal in strength but opposite in direction to an action force.
What happens when an object exerts a force on another object?
The second object exerts an equal and opposite force on the first object.
How do you identify the action-reaction forces in an interaction?
To identify a pair of action-reaction forces, first identify the interacting objects A and B, and if the action is A on B, the reaction is B on A.
Why do objects that experience the same amount of force accelerate at different rates?
A given force exerted on a small mass produces a greater acceleration than the same force exerted on a large mass.
Why don't action-reaction forces cancel each other?
Action and reaction forces do not cancel each other when either of the forces is external to the system being considered. Conversely, forces exerted within a system do cancel each other.
How does a horse-cart system accelerate?
If the horse in the horse -cart system pushes the ground with a greater force than it pulls on the cart, there is a net force on the horse, and the horse-cart system accelerates.
What must occur in every interaction between things?
For every interaction between things, there is always a pair of oppositely directed forces that are equal in strength.