# Pulling on a cylinder

1. Oct 18, 2009

### Sumbhajee

1. The problem statement, all variables and given/known data
A spool of thin wire (with inner radius r = 0.45 m, outer radius R = 0.60 m, and moment of inertia Icm = 0.91 kg*m2 pivots on a shaft. The wire is pulled down by a mass M = 1.35 kg. After falling a distance D = 0.52 m, starting from rest, the mass has a speed of v = 79.900 cm/s. Calculate the energy lost to friction during that time. http://schubert.tmcc.edu/res/msu/physicslib/msuphysicslib/20_Rot2_E_Trq_Accel/graphics/prob22_pulleyD.gif

2. Relevant equations

3. The attempt at a solution

I have been having a lot of trouble with these rotation problems and I am not sure where to start on this. Any assistance would be appreciated.

Last edited by a moderator: Apr 24, 2017
2. Oct 18, 2009

### Delphi51

Consider the types of energy involved. You start with the gravitational PE of the mass, and as it falls you lose that and get KE plus the rotational energy of the spinning spool. Write out a law of conservation of energy for those.