Physics
posted by Brittany on .
A turntable of radius 2m rotates freely about a fixed vertical axis. A child 19 kg is standing on the turntable right at the outer edge and the system is initially rotating at an angular speed of 0.5 rev/s. The child then moves to position 1m from center of the turntable. what does the urntable angular speed become? The moment of inertia is 400kgm^2.

conservation of momentum
29*2^2*.5+400*.5=29*1^2*w + 400*w
solve for w, in revs/sec 
I don't really understand we use I1w1=I2w2?
but according to your equation its
mr^2+Iw = mr^2+Iw ... which is equivalent to I+L = I+L < i don't get this part?
and the answer is 0.568 rev/s which according to your way is right but its 19 instead of 29. 
i mean..
mr^2w+Iw = mr^2w+Iw ... which is equivalent to L+L = L+L 
The moment of inertialfor the kid is mass*distance^2.
sorry about the 29. 
ohh okies thanks for clearing that up (: