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A circular turntable rotates at constant angular speed about a vertical axis. There is no friction and no driving torque. A circular pan rests on the turntable and rotates with it; see Fig. The bottom of the pan is covered with a layer of ice of uniform thickness, which is, of course, also rotating with the pan. The ice melts but none of the water escapes from the pan. Is the angular speed now greater than, the same as, or less than the original speed? Give reasons for your answer

A circular turntable rotates at constant angular speed about a vertical axis. There is no friction and no driving torque. A circular pan rests on the turntable and rotates with it; see Fig. The bottom of the pan is covered with a layer of ice of uniform thickness, which is, of course, also rotating with the pan. The ice melts but none of the water escapes from the pan. Is the angular speed now greater than, the same as, or less than the original speed? Give reasons for your answer

Grade:10

1 Answers

Jitender Pal
askIITians Faculty 365 Points
8 years ago
When the ice converts into water, due to the action of centrifugal force the water will accumulate along the walls of pan (refer figure below).
235-1374_1.PNG
This increases the rotational inertia of the rotating pan and makes it harder for the Pan to rotate. No external torque acts on the system during the process of melting and therefore the angular momentum of the system should be conserved. To accomplish this, the increased rotational inertia of the system should be compensated by decrease in angular speed.

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