A hockey puck of mass m is attached to a string that passes through a hole in the center o...

A hockey puck of mass m is attached to a string that passes through a hole in the center of a table, as shown in Figure. The hockey puck moves in a circle of radius r. Tied to the other end of the string, and hanging vertically beneath the table, is a mass M. Assuming the tabletop is perfectly smooth, what speed must the hockey puck have if the mass M is to remain at rest?

FIGURE