physics

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A 1-kg mass hangs by a string from a disk with radius 5.1 cm which has a rotational inertia of 5 × 10-5 kg•m2. After it falls a distance of 1.4 meters, how fast is it going?
What is the angular velocity of the disk?

  • physics -

    Is the string wound around the disc, so that the disc spins when the weight falls?

    If so, then use

    M g H = (1/2)M V^2 + (1/2) I*(V/R)^2

    to solve for V, the velocity when H = 1.4 m.

    The second term on the right is the disc's rotational kinetic energy. V/R is the angular velocity that they want.

  • physics -

    Thanks a lot

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