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Calculate the acceleration of the elevator

  1. Jan 28, 2007 #1
    1. The problem statement, all variables and given/known data
    A person stands on a bathroom scale in a motionless elevator. When the elevator begins to move, the scale briefly reads
    only 0.78 of the person’s regular weight.
    a. Calculate the acceleration of the elevator.
    b. Find the direction of acceleration.

    2. Relevant equations
    Sum of forces.

    3. The attempt at a solution

    I know the equation is F_normal-mg=ma but don't understand how it was derived.
  2. jcsd
  3. Jan 28, 2007 #2
    The normal force points in the y direction and is opposite to the weight of the person (mg). Newtons law says that the sum of all forces = ma. Since the elevator is only moving in y direction, the only component of the net force is the component in the y direction. Put the 2 together and you have F_n -mg = ma

    Now that you know this...what are your thoughts on the problem?
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