Is the momentum of a system always conserved?

Question

Is the momentum of a system always conserved? Explain by giving examples, please?

Ok, but do any of you have a specific example of when momentum would not be conserved? Would a good example be a boat in water? Since the velocity would be affected by the water resistance?

Answer 1

It (the total momentum of everything in the system) is if the system is isolated from outside forces. But if a force from outside the system acts on any part of the system it can change the momentum of the system.

Answer 2

I would agree with Steve, but would add the stipulation that the system must be isentropic; in other words, if there are heat losses due to friction, etc within the system, then I would not expect the laws of momentum conservation to behave as predicted by the classic form.

ADDED:

Lisa - Sure, that's an excellent example. Or an ice skater spinning. Really anything that moves that's within our experience does not strictly obey the momentum conservation laws. There are always losses. Otherwise, we would be able to make a perpetual motion machine. Entropy tends to increase over time, which means things don't stay neat and tidy.

Answer 3

In actual existence there is not any collision that's "completely elastic" because of this some potential is lost (exchange in momentum) generally in style of heat. Secondly there is not any floor that's frictionless, so some potential is often lost in friction. in case you get the impressive sum of momentums below the preliminary then the above clarification solutions. although, while you're starting to be very final momentum greater beneficial than the preliminary, there is a few measurement errors.