Subject: Followup question: Rotational Dynamics-hamster and wheel

The original question was:

"After getting a drink of water, a hamster jumps onto an exercise 
wheel for a run.  A few seconds later the hamster is running in 
place with a speed of 1.4 m/s.  Find work done by the hamster to get 
the exercise wheel moving, assuming it is a hoop of radius 0.13 m 
and mass 6.5 g.

[Difficulty]
the hamster's mass

[Thoughts]
By work-energy theorem, the amount of work done is equivalent to the 
finial kinetic energy minus the initial kinetic energy.  Since the 
initial kinetic energy is 0, it follows that the work is equivalent 
to the final kinetic energy.  K = (1/2)mv^2, v = 1.4 m/s, m = 6.5 g 
+ hamster's mass, which is unknown.  The radius is not used.  I know 
the moment of inertia I of a hoop is mr^2, and m = 6.5 g and r = 
0.13 m.  Please help me."

The reply was:

"With this kind of problem I'm assuming you have studied
rotational kinetic energy, which is what you need to
think about in this problem, for which the moment of inertia
is one of the key parts.

	John Link, Moderator MadSci Network"

New questions/thoughts:

Well, I know the momentum of the system is conserved; that's it, the initial 
momentum mv of the hamster running towards the wheel should equal to the final 
momentum of the system with both the hamster and the wheel.  However, we are 
not able to use this approach because the mass of the hamster and its speed 
(assuming constant) when it was running towards the wheel are unknown.

By the way, what if the speed of the hamster is not constant, but with a 
constant acceleration a?  Would the conservation of momentum still work (since 
the initial momentum of the hamster is not constant, or can this be done using 
calculus (like using integrals to sum up the total work of a system if both 
force and position are not constant)?  This physics book I am reading does not 
involve the implement of calculus, but I am studying a separate calculus 
textbook on my own. 

Re: Followup question: Rotational Dynamics-hamster and wheel