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## Homework Statement

A disk-shaped merry-go-round of radius 2.63 m and mass 155 kg rotates freely with an angular speed of 0.686 rev/s. A 59.4 kg person running tangential to the rim of the merry-go-round at 3.99 m/s jumps onto its rim and holds on. Before jumping on the merry-go-round, the person was moving in the same direction as the merry-go-round's rim.

(a) Does the kinetic energy of the system increase, decrease, or stay the same when the person jumps on the merry-go-round?

increase

stay the same

decrease

(b) Calculate the initial and final kinetic energies for this system.

Ki = kJ

Kf = kJ

## Homework Equations

KErot= 1/2*Iw^2

I=1/2mr^2

## The Attempt at a Solution

a) I would think it should increase but I am probably wrong, lol.

b) The merry-go-round initially is just spinning so I trued finding the KE using the 1/2*I*w^2 formula so I got 1/4*m*r^2*w^2and I came up with 4.98 kJ and that's the wrong answer... is there something I did wrong?

I don't have any idea how to find the KEf. Can I assume that its the rotational KE of the merry-goround plus the KE of the guy jumping on it?