Question #22d6b

2 Answers
Oct 27, 2017

I tried with an example...

Explanation:

Imagine you try to push an object, say a heavy wardrobe, on a icy road.
Here the trick is the mass....you give a sharp push and...
You will "feel" something pushing you and making you slide away. Ok, probably you will even fall but this is not the point, the idea is that in the action-reaction game you do not have necessarily cancellation. In this case the reaction of the wardrobe will put you in movement and basically it was your initial sharp push that caused it!!!

In space the astronauts use this idea to move around (and if you think of it even our airplanes or rockets do the same throwing “stuff” behind them) throwing a small object (action) in the opposite direction receiving a reaction that propels them in the opposite direction.

So basically we must remember that action-reaction doesn't necessarily means cancelation.
Hope I didn’t confuse you even more…!

Oct 27, 2017

The key to understanding Newton's 3rd Law is that the action/reaction pair of forces always act on different objects.

Explanation:

A swimmer pushes off of a wall.

Kahn Academy, adapted from from Openstax College Physics

In this scenario, Newton's 3rd Law says that there is a pair of forces, with equal magnitudes and opposite directions. There is the force of the swimmer's feet on the wall and the force of the wall on the swimmer's feet.

The forces don't cancel because they are acting on two different objects . The feet push the wall and the wall pushes the feet.