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.
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.
Click here to return to the Physics Archives
Update: June 2012