Energy and work,- pulley?

Question

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?

Answer 1

School questions they keep as simple as possible.

Of course the mass of the pulley is part of the equation, if it is being lifted. Of course friction and the weight of the rope are important.

You have a lot of specific questions that cannot be answered without a clear diagram of the pulley system you are talking about.

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Answer 2

Usually the mass of the pulley and rope are so insignificant vs the loads that they are pulling. This will not add to the kinetic energy. The only kinetic energy you get out of this system is the kinetic energy you put in to it.

     It will either be in the form of moving the load or heat from friction. If the pulleys and rope are significant in comparison to the load, then the velocity slows down proportionally to make the results to the equation KE= 1/2 m v^2  unchanged.