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Child jumping on merry go round
A 15 kg child runs at a speed of 5.2 m/s tangent to the edge of a playground merry-go-round and leaps horizontally onto the ride. The merry-go-round is 3.0 m in diameter and has a moment of inertia of 120 kgm^2. It was initially moving at an angular speed of 12 revolutions per minute. What is the new angular speed in rpm after the child jumps on?
Can I just use conservation of energy to compare the kinetic energy of the child and the rotational of the merry-go-round, to the system of both of them?
Customer support service by UserEcho
You may use that method, however, you may run into trouble with actually implementing it. I suggest using conservation of angular momentum because it is much simpler (visually). If you use this method:
1. find the final moment of inertia from the different moment of inertia given to you for the kid and the merry go around.
2. Use I_i*w_i = I_new*w_f to find w_f (angular speed), where I_new if the final moment of inertia.