1.

A uniform disc of mass 100 kg and radius 2 m is rotating at 1 rad/s about a perpendicular axis passing through its centre of the disk suddenly jumps to a point which is 1 m from the centre of the disc. The final angular velocity of the boy (in rad/s) is

Answer»

0.77
0.5
41
2

Solution :Angular momentum is CONSERVED as there is no external TORQUE.
So, `I_(1) omega_(1) = I _(2)2 omega_(2)`
`rArr ((1)/(2)M_(disc)xxR_(disc)^(2)) omega_(1) = ((1)/(2)M_(disc)R_(disc)^(2)+M_(boy)R_(boy)^(2))omega_(2)`
`rArr ((1)/(2)xx100xx2^(2))xx1=((1)/(2)xx100xx2^(2)+60xx1^(2))xxomega_(2)`
`rArr omega_(2)= (200)/(200+60) = 0.77 " rad"-s^(-1)`


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