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Consider two atoms A and B, with A at rest and B in motion towards A. As soon as B is in the atomic field of A, will it stop with its energy going into B or will it just move up to a postion where there is equillibrum between the forces of both the atoms and then move A with itself, but the whole mass will now move with a lesser velocity, i.e. the momentum just gets rearranged?

When I look at the above scenario, I find it easy to agree with the second option (the rearrangement of momentum), but it looks like the first option of stopping will never happen, because it can repel back only if it goes beyond the point of equilibrium, which doesn't look like it will happen.

Even if it happens, how will A gain all of the force of B, as A will experience a atomic force from B which will balance some amount of the force of A?

please explain

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  • $\begingroup$ I'm not sure what you're asking. What is an "atomic field"? What is the "force of B"? If you're just asking whether the outcome of a collision is one body stopping and the other moving or both moving, then that depends on the masses of the objects -just apply the formulae for elastic collision. $\endgroup$
    – ACuriousMind ♦
    Commented Jan 24, 2016 at 15:06
  • $\begingroup$ well by atomic field i mean the range of the atomic force exerted by the charges in an atom $\endgroup$
    – Faiz Iqbal
    Commented Jan 24, 2016 at 15:07
  • $\begingroup$ The range is infinite $\endgroup$
    – Suriya
    Commented Jan 24, 2016 at 15:12
  • $\begingroup$ To know whether its moving or not you have to apply the conservation of momentum and conservation of energy $\endgroup$
    – Suriya
    Commented Jan 24, 2016 at 15:13
  • $\begingroup$ @pablo well that sounds intresting , it looks like that how much an object sinks into another object atomic field depends on the movin objects velocity right ? $\endgroup$
    – Faiz Iqbal
    Commented Jan 24, 2016 at 15:16

1 Answer 1

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Newton's third law says the the force on A due to B is equal and opposite to the force on B due to A. This in turn means that the changes of momentum of A and B are the same in magnitude but opposite in direction. This is how the momentum becomes rearranged. B loses some momentum and A gained an equal amount.

So when two atoms collide you can think of their electrons shells interacting. This interaction might well form a bond between the atoms but the combined amount of momentum they carried will not change. You can think of one of the atoms slowing down whilst the other speeds up until they are both travelling at the same velocity.

PS Be careful about using energy, force and momentum as though they are interchangeable words.

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  • $\begingroup$ then can you please explain how does sometimes the momentum of one objec become zero during some elastic collision , in case your half momentum theory doesnt comply to this result ! $\endgroup$
    – Faiz Iqbal
    Commented Jan 24, 2016 at 15:39
  • $\begingroup$ @FaizIqbal Farcher didn't say what happens after they have the same velocity. At that point they could be too squished together and so continue to exert forces on each other. These additional forces could slow down the incoming particle so it moves slower than the common velocity and meanwhile speed up the other particle to start moving faster than the common velocity. Another example is two particles coming in together equally. Eventually they both come to rest, but then they start moving back outwards the way they came in, leaving with an opposite momentum to what they came in with. $\endgroup$
    – Timaeus
    Commented Jan 24, 2016 at 18:11
  • $\begingroup$ @Timaeus so , do you mean that the digging of the moving atom into the stationary atoms , really depends on the velocity ? does the mass also play a role ? if yes ? then how ? $\endgroup$
    – Faiz Iqbal
    Commented Jan 25, 2016 at 3:58

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