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A boy is seated in as revolving chair re...

A boy is seated in as revolving chair revolving at an angulr speed of 120 revolutions per minute. Two heavy balls from part of the revolving system and the boy can pull the balls closer to himself or may push them apart. If by pulling the balls closer, the boy decreases the moment of inertia of the system from `6 kg-m^2 to 2kg-m^2` what wil be the new angular speed?

Text Solution

Verified by Experts

The correct Answer is:
C
`omega_1=120rpm=120xx((2r)/60)`
`=-4rrad/s`
`I_1=6kg-m^2,I_2=2kg-m^2`
since two balls are inside the system, total exterN/Al torque =-0`
Therefore `I_1omega_1=I_2omega_2`
`rarr 6xx4r=2omega_2`
`rarr omega_2=12r rad/s`
`=6rev/s `
`=360rev/minute
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