# Homework Help: Conservation of Linear, Rotational Mechanical Energy

1. Nov 29, 2011

### mrshappy0

1. The problem statement, all variables and given/known data
Attached is a photo of the linear and rotational dynamics exercises. Times t1 and t2 were measured. For the linear exercise the top block was pushed with an initial force along the FRICTIONLESS level plane. It passed the timing device twice. Once through and once on the way back. Would the mechanical energy be conserved in this situation? For exercise two the disk was held at rest and released. Gravity applied torque at a set radius. The angular velocity was determined for times t0, t1, and t2. The disk was flat (level) with surface. Would mechanical energy be conserved for this?

2. Relevant equations

MErotational=IW2/2

MElinear=MV2/2

3. The attempt at a solution

My data shows a small change in MEnergy. Does this imply that it is conserved but not perfectly due to air resistance, not perfectly frictionless, etc...

For the second section, I thought mechanical energy was not conserved when an external torque is applied. In this case gravity is applying external torque.

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