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A playground merry-go-round has a disk-shaped platform that rotates with negligible friction about a vertical axis. The disk has a mass of 240 kg and a radius of 1.4 m. A 33- kg child rides at the center of the merry-go-round while a playmate sets it turning at 0.20rpm. If the child then walks along a radius to the outer edge of the disk, how fast will the disk be turning?

  • physics -

    conservation of momentum applies, in this case, angular momentum.

    Diskmomentum=I*w
    Boy momentum=33*r*2PI*.2/60

    set them equal, w will be in rad/sec

    disk moment of inertial is 1/2*240*r if you didn't know. Thin disk.

  • physics -

    the answer has to be in rpm, so does that mean that i'm not supposed to multiply by 2PI/60?

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