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An 800g object collides head-on with a 2400g object, compressing a spring fastened to the 2400g object as it does so. Is momentum conserved as the spring is being compressed?

Are you referring to the linear momentum of the 800g object, the linear momentum of the 2400g object, both objects taken together, or the mass1/mass2/spring system's total linear momentum? Remember that Newton's laws say that: a body which is at rest or in a uniform state of motion tends to stay in its state unless acted upon by some net external force, in which case its momentum will change with time. So one must carefully define the system before this question can be answered.


Of course, total momentum is always conserved, which is how one can figure out even more about what happens in this particular problem.

Arthur Smith

Yes, the total linear momentum is conserved...but the question was "Is momentum conserved...?" And of course, the momentum of the particle which is slowing down is NOT conserved. Since there are several "kinds" of momentum here, one cannot answer the question as (literally) posed.


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