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Posted by on Wednesday, October 27, 2010 at 8:59pm.

A 70kg man stands on a bathroom scale in an elevator. As the elevator starts moving, the scale reads 90kg
Is the elevator acceleration up or down, is the elevator moving up or down?

  • physics - , Wednesday, October 27, 2010 at 9:04pm

    i think you mean it's weight (units in N), because mass is constant.
    anyway, since the weight increased, the elevator accelerates and moves up. :)

  • physics - , Wednesday, October 27, 2010 at 9:07pm

    Force up on man - weight of man = m a up
    F scale - m g = m a
    Fscale = 90*9.8

    90*9.8 - 70*9.8 = 70 a

    a = 20*9.8 /70
    the acceleration is up
    since we started from rest, we will be moving up but have not gained any speed yet

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