How do friction and rotation affect tension in pulley systems?

[ual8658]

[mentor's note: Spilt from https://www.physicsforums.com/threads/tension-questions.852525]

How does friction in a pulley or a rotating pulley change the uniform tension in a rope that was present in an ideal situation? Thanks!

 

[Nugatory]

[mentor's note: Spilt from https://www.physicsforums.com/threads/tension-questions.852525]

How does friction in a pulley or a rotating pulley change the uniform tension in a rope that was present in an ideal situation? Thanks!

If the pulley is not accelerating, then the total force on it is zero. So what are the forces acting on the pulley? Tension in the rope coming in from one side, tension in the rope coming in from the other side, frictional force... They have to sum to zero.

Note that this is exactly the same procedure that you'd go through with an ideal frictionless pulley as well; it just so happens that in that case the frictional force is zero so doesn't contribute to the sum.

 

[ual8658]

So if there were friction how would the tension be affected? Would it decrease, increase, become non-uniform? And if the pulley itself rotates, how does tension change?