A student sits on a stool that is free to rotate about a vertical axis. He holds out his arms horizontally, with a 4-kg weight in each hand. The stool is set in rotation with angular speed of 0.5 revolution per second. Calcualate the angular speed of the student is 90 cm and his rotational inertia is 7kg `m^(2)`.
[Hint: Use conservation principle]

A wheel is rotating at the rate of 10 revolutions per second about an axis about which the radius of gyration is 0.2m. If the mass of the wheel is 5 kg then its rotational kinetic energy is

A wheel is rotating at the rate of 10 revolutions per second about an axis about which the radius of gyration is 0.2m. If the mass of the wheel is 5 kg then its rotational kinetic energy is

A circular disc of 49 kg and radius 50 cm is rotating at a speed of 120 rotations per minute. Calculate its kinetic energy if is moment of inertia about the axis of rotation is 1/2 mr^(2) .

A 0.5 kg of mass is rotated in a horizontal circle of radius 20cm. Calculate the centripetal force acting on it , If angular speed of revolution is 0.8 rad/s.

(a) A child stands at the centre of a turntable with his two arms outstretched. The turntable is set rotating with an angular speed of 40 rev/min. How much is the angular speed of the child if he folds his hands back and thereby reduces his moment of inertia to (2)/(5) times the initial value? Assume that the turntable rotates without friction. (b) Show that the child.s new kinetic energy of rotation is more than the initial kinetic energy of rotation. How do you account for this increase in kinetic energy?

(a) A child stands at the centre of a turntable with his two arms outstretched. The turntable is set rotating with an angular speed of 40 rev/min. How much is the angular speed of the child if he folds his hands back and thereby reduces his moment of inertia to 2/5 times the initial value ? Assume that the turntable rotates without friction. (b) Show that the child’s new kinetic energy of rotation is more than the initial kinetic energy of rotation. How do you account for this increase in kinetic energy?

(a) A child stands at the centre of a turntable with his two arms outstretched. The turntable is set rotating with an angular speed of 40 rev/min. How much is the angular speed of the child if he folds his hands back and thereby reduces his moment of inertia to 2/5 times the initial value ? Assume that the turntable rotates without friction. (b) Show that the child’s new kinetic energy of rotation is more than the initial kinetic energy of rotation. How do you account for this increase in kinetic energy?