# Minimum velocity at the top of an object on a rope vs attached to a rigid body?

When working through a physics problem, I realized there's a fundamental difference between when an object is spinning in a circle and is attached to some rigid object such as a beam fixed to an axle vs a non-rigid object such as a rope.

When looking at the minimum velocity at the top to continue moving in a circle, with an object such as a rope, the minimum velocity is $\sqrt{rg}$ to get around the top. But with an object fixed to a rigid object, the velocity at the top can be zero and it will continue to move in a circle. I feel like it has something to do with the rigid object providing a normal force that counteracts gravity which a rope doesn't, but I'm not sure how this provides the difference between minimum clearing velocity at the top.

• So what's the question exactly? Commented Oct 23, 2016 at 21:38
• @EL_DON why minimum velocity is different in the two cases? Commented Oct 23, 2016 at 21:53
• Possible duplicate of Tension in string and light rod in vertical circle. Commented Oct 24, 2016 at 3:07