Pulley with mass

1. Jul 27, 2008

devanlevin

in all energy and work questions i have had till now, the mass of pulleys have not been taken into account, if they had, would the system's kinetic energy have increased?
it seems to me that a pulley with mass would have velocity and acceleration and therefore would have its own kinetic energy,
if the system started from resting point, then the total work would be W=EK1, ie kinetic energy of the system, whereas with a pulley with mass W=EK1+EK2 ie knetic energy of the system as it was and kinetic energy of the pulley, the system as a whole will manage the same work with less EK1, is this logical?? what does it mean? will it pass the same distance but with lesser velocity?
is this point only valid if there is friction between the pulley and the rope or would this still affect the rest of the system if there was no friction whatsoever?

2. Jul 27, 2008

mukundpa

What will make the pulley rotate?
If the pulley will rotate, will it have kinetic energy?