Question

Newton's third law of motion states that for every action there is an equal and opposite reaction. Do the action force and the reaction force act on the same body or on two different bodies?

Hint:

Identify which object each force acts on. The action and the reaction of Newton's third law always act on two separate bodies, never on the same one.

Answer 1

Step 1: Newton's third law says that whenever one body exerts a force, the action, on a second body, the second body exerts an equal and opposite force, the reaction, back on the first body.

Step 2: The key point is that these two forces never act on the same object. The action force acts on body B due to body A, while the reaction force acts on body A due to body B.

Step 3: Because the two forces act on two different bodies, they do not cancel each other out even though they are equal in magnitude and opposite in direction. If they acted on the same body, nothing would ever move, since the net force on that body would always work out to zero.

Step 4: A simple example is a swimmer pushing water backward with the hands, the action, while the water pushes the swimmer forward with an equal force, the reaction. The action acts on the water, and the reaction acts on the swimmer, so the swimmer actually moves forward.

So Newton's third law applies to a pair of forces acting on two different bodies, known as an action reaction pair.