Question

I have a question regarding to the rotating rod PC example in lecture 21. Professor said that the torque is relative to P is 0,but why? I thought there should be mgcosø at C that renders torque to be non-zero

Answer 1

If we were rotating this on a table then the idea will hold.

Answer 2

Yes exactly thought professor was talking about nailing the rob on the wall. But I was wrong he meant on a fricitonless plane.