# What rotates a disk hung at center of mass when it is tilted?

when a disk is hung by a string attached to the center of mass point is tilted, what is making it fall and become horizontal again

Note the white line is a light string.

Here $$Torque_{net} = 0$$ and $$F_{net} = 0$$ so why does it rotate?

• Does this really happen? Commented May 2, 2022 at 5:29
• I don't think "hinged" is the word you want there. en.wikipedia.org/wiki/Hinge Commented May 2, 2022 at 9:49
• @CarlWitthoft I don't think so: physics.stackexchange.com/questions/13474/… The OP's scenario is not the same. See-saws on the play ground don't sit inherently balanced. I also believe the OP's scenario is not quite what they think it is. They may be thinking it is like a propeller balancer but the scenario described is dependent on how the string is connected to the plate and with most methods the string is bent when the plate tilts Commented May 2, 2022 at 13:37
• @DKNguyen thanks for pointing out how it can differ Commented May 2, 2022 at 14:00
• also related, physics.stackexchange.com/questions/247510/… Commented May 3, 2022 at 12:08