Question

Which one of the following pairs of forces is not valid example of action and reaction to which Newton’s third law of motion applies?

Answer 1

A. The centripetal force holding a satellite in orbit round the Earth and the weight of the satellite.
B. The forces of repulsion experienced by each other of two parallel wires carrying currents in opposite direction.
C. The forces of attraction felt by each of two gas molecules passing near to each other.
D. The forces of attraction between an electron and a proton in a hydrogen atom.
E. The forces of repulsion between an atom in the surface of a table and an

Answer 2

B and E is obviously action-reaction force. Can anyone give analysis on A C and D?
I never heard action-reaction force to attract (C, D), but then again centripetal force holding a satellite came from the weight of the Earth not the satellite.

Answer 3

@satellite73

Answer 4

gravitation is an example of action reaction force to attract!

Answer 5

Centripetal force is the role played by the weight of the satellite.. !!

Answer 6

and your E is incomplete!

Answer 7

Hulk are you stuck or something? lolzzz :D

Answer 8

Action and reaction don't act on the same body. For example, if I grab somebody's collar and pull them towards me, I can feel the pull towards them. These two 'pulls' form an action reaction pair. Here, Action=me pulling him (i.e. a force on HIS body) and Reaction=me being pulled towards him (i.e. a force on MY body). So you see, two different bodies.

I just gave you an example of action-reaction forces *attracting* two bodies. Now coming to the problem at hand-
Look at option C. The situation here is similar to the example I just gave you. It's like gas molecule A is pulling the gas molecule B towards it by it's collar. Consequently, A gets pulled towards B too (it's feeling that force). Notice how these two forces are acting on two different bodies. They are therefore an action-reaction pair.
Option D is also exactly similar to option E. Proton is yanked towards the electron, electron yanked towards the proton--->forces on different bodies-->action-reaction pair.

Now for option A. The centripetal force in this case is nothing but the gravitational force. And weight is nothing but a measure of the gravitational force. So essentially, the two forces here are the same. So this is the answer.
You know which two forces would form an action-reaction pair in this case? The force that pulls the satellite towards the earth and the pull felt by the earth towards the satellite (again, forces acting on two different bodies).

Answer 9

Isn't D nuclear force?

Answer 10

no it's not. It's electric force. nuclear forces are those which hold the constituents of the nucleus (protons and neutrons) together.