Puck on a string through a hole with hanging mass

[vibha_ganji]

Hello! This is a problem from Halliday Resnick Krane (Chapter 4: Problem #15). “A puck is moving in a circle of radius r0 with a constant speed v0 on a level frictionless table. A string is attached to the puck, which holds it in the circle; the string passes through a frictionless hole and is attached on the other end to a hanging object of mass M.” What I don’t understand is how this system works. How does hanging a heavy mass through a table make the mass m on the table spin in a circle?

 

[hutchphd]

Someone has given it an initial push sideways to make it circle as described. After a small time, absent friction, a steady state can ensue.

 

[Falgun]

The weight of the mass M causes tension in the string. The tension then acts as the centripetal force required for circular motion. As @hutchphd mentioned an initial push is required to start the circular motion.