IIT JEE , AIEEE Forum - Physics , Mechanics - Rotation- please explain.

rahulraj1

A kid of massM stands at the edge of a platform of radius R which can be freely rotated about its axis . the M.I of the platform is I. The systemis at rest when a freind throws a ball of mass m and the kid catches it .If the velocity of the ball is v horijontly along the tangent to edge of the platforn when it was caught by the kid,find the angular speed of the platform after the event.

karthik2007

Anup

solve it by conservation of angular momentum..........

mvR=(I+mR²+MR²)w

w=mvr/(I+MR2+mR2)

I+MR2+mr2 is the moment of intertia of the system after the boy catches the ball.....

nishi.tiwari

A kid og mass Mstands on the plateform having R radius has a MOI. he catches a ball wid horizontal velocity v thorwn to him.

therefore, if we take all the bodies as a system,

mvR={1+(m+M)R²)

theMOI of kid & ball abt axis=(m+M)R²

=mvR/1+(m+M)R²

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