Newton's Third Law

action force

one of the pair of forces described in Newton's third law. The ___ is equal in strength and opposite in direction to the reaction force. The ____ acts simultaneously on whatever is exerting the reaction force.

Agent

the source a force. Examples: if you push a cart with your hand, your hand is the _____; your weight is the result of the forceEarth exerts on you, so Earth is the agent of the gravitational force on you that is your weight.

Force

A vector quantity that is a measure of the push or the pull that acts on an object or system because of an interaction between the object and its environment

Interaction

a mutual action between objects where each object exerts simultaneously an equal-in-magnitude and opposite-in-direction force on the other.

Interaction pair force noration

A standard notation often used with interaction forces is F agent on system . The forces involved with your interaction with the earth gives you weight and also pulls on the earth. These forces are an interaction pair, and, following this convention would be written F earth on you = - F you on earth

Newton's third law

any force is an interaction between two things. Newton's third law states that forces always come in pairs, that these paired forces are always equal in magnitude, opposite in direction, occur simultaneously, and always at on different things. Because each of the forces in the interaction acts on the other object, these forces can NEVER produce a net force and can NEVER cancel each other.

Reaction force

the force that is equal in strength and opposite in direction to the action force and which acts simultaneously on whatever is exerting the action force

System or object

the "thing" upon which forces acts. The terms "system" or "object" are both used, and, for our purposes, are interchangeable. Sometimes "system" ,may refer to a collection of object with more than one part, such as describing a system of two billiard balls, a system of you and the earth, or a system of two interacting lab carts.

Why do forces always occur in pairs?

a force is always part of a mutual action that involves another force.

What happens when an object exerts a force on another object?

Newton's third law states that whenever on object exerts a force on a second object, the second object exerts an equal and opposite force on the first object.

How do you clearly identify the interacting forces in an interaction?

To identify a pair of action- reaction forces, first identify the interacting objects A & B, and if the action is A on B, the reaction is B on A

How does Newton's second law relate acceleration to mass when the force is constant?

For a constant force, an increase in mass will result in a decrease in the acceleration

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 interaction forces cancel each other? After all, they are equal force in opposite directions!

Action and reaction forces can do not can cancel each other when either of the forces is external is exerted to the system being considered