What Forces Act on a Ball Attached to a Massless Rod in a Vertical Loop?

AI Thread Summary
In a vertical loop, a ball attached to a massless rod experiences forces that include gravity and the normal force exerted by the rod. At the top of the loop, the normal force acts upward while gravity acts downward, contributing to the centripetal force required for circular motion. The rod can either push or pull the ball depending on its speed, which influences the necessary centripetal force. At the bottom of the loop, the rod exerts a tension force that pulls the ball upward. Understanding these forces is crucial for analyzing the motion of the ball in the vertical circle.
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Homework Statement



A ball of mass m is attached to a massless rod and is suspended from a frictionless pivot. It is moving in a vertical circle or Radius R such that it has speed v1 at the bottom. The ball is in a vacuum. Find an expression for the force exerted by the rod at the top of the loop as a function of m, v1, g, and R. This is more of a general question. Not looking for an answer to the entire problem. I'm just wondering if the rod exerts a normal force if it is massless. If so, at the top there is a Normal force acting upward and gravity and tension acting downward, correct?
 
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As the mass is attached to the rod, the rod can either push or pull the ball, but there is only one force it exerts on the ball. This force and the weight of the ball keeps it moving along the vertical circle.

ehild
 
ehild said:
As the mass is attached to the rod, the rod can either push or pull the ball, but there is only one force it exerts on the ball. This force and the weight of the ball keeps it moving along the vertical circle.

ehild

So at the top, we have a normal force pushing the ball up, and at the bottom, a tension force pulling the ball?
 
At the top you can have both a pushing force or a pulling one, it depends on the speed which determines the centripetal force needed.

At the bottom, the rod pulls the ball upward.

ehild
 

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