Suppose the platform with the kid in the previous problem is rotating in anticlockwise direction at an angular speed w. The kid starts walking along the rim with a speed u relative to the platform also in the anticlockwise direction. Find the new angular speed of the platform.
Given:
Angular velocity of the wheel before kid starts walking = w
Angular velocity of the wheel after walking = 
Speed of kid relative to platform= u
From the inertial frame of reference, the system is moving with the speed = 
Since no external torque is acting on the system
Therefore,
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