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Jul 17, 2008

Problem 6/120



Wheels A and B differ only in the values of their mass moments of inertia. Carefully read the question to understand the distribution of mass for each wheel.
  • For wheel A, all mass is concentrated at a point at its center (a PARTICLE). The spokes and rim only serve to support the particle and effectively add no mass or mass moment of inertia to the wheel.
  • For wheel B, all mass is distributed around the hoop (a THIN RING for which the mass moment of inertia is given in an appendix in the textbook).
Think about your results after you complete the problem. Which wheel is moving faster after traveling the same distance along the incline? Why? Do these results agree with your intuition?

3 comments:

ckearney said...

My solution shows that V_a = V_b/sqrt(2). My intuition says that B should have more momentum.. is it true that B will be harder to stop, even though it's not accelerating as fast as A?

CMK said...

Your conclusion is correct: all of the original potential energy for A goes into translational energy, whereas the same PE for B goes into both translational and rotational energy. Therefore, B is moving more slowly than A.

For the same translational speed, B will require more force to stop than A over the same amount of time.

ckearney said...

Great. Thank you.