\"A child stands beside a 200 kg, 3 m merry-go-round. How much force must she ex

Question

"A child stands beside a 200 kg, 3 m merry-go-round. How much force must she exert tangent to the edge of the merry-go-round to spin it at 1 rev/s in 30 seconds?"

If a merry-go-round exactly like the one mentioned in the previous problem was spinning at 1 rev/s and you dropped a 25 kg sand bag vertically onto the edge of the platform at a radius of 3 m, what would the new angular speed become?

I don't need help with the first problem provided, but I need help withe second problem that is based off of the first problem.

Explanation / Answer

apply conservation of angula momentum ;

I1 1 + I2 2 = ( I1 + I2 ) ;

1 /2 M r^2 1 + mr^2 2 = ( 1 /2 M r^2 + mr^2 ) ;

1 /2 * 200 * 3^2 * 1 + 25 * 3^2 * 0 = [1 /2 * 200 * 3^2 + 25 * 3^2 ]   ;

or = 0.8 rev / s <----------------ans

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