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Physics

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A bullet (m = 0.0250 kg) is fired with a speed of 92.00 m/s and hits a block (M = 2.50 kg) supported by two light strings as shown, stopping quickly. Find the height to which the block rises.
Find the angle (in degrees) through which the block rises, if the strings are 0.540 m in length.

  • Physics - ,

    At collision use conservation of momentum
    Mbullet Vi bullet = (Mbullet+MBlock)V

    solve for V, the speed of the block with the bullet in it

    calculate kinetic energy
    (1/2) m v^2

    that becomes potential energy when the block stops
    m g h
    so
    v^2 = 2 g h
    solve for h
    now get angle
    hypotenuse is L, length of string
    T = string angle from vertical
    cos T = (L-h)/L
    solve for T

    by the way you can approximate cosine for small angles
    Cos T = 1 - T^2/2
    1 - T^2/2 = 1 - h/L
    T^2 = 2 h/L
    T = sqrt(2 h/L)
    note T will be in RADIANS if you do that

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