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Homework Help: Calculate the height of a building using scale measurements

  1. Nov 16, 2011 #1
    1. The problem statement, all variables and given/known data
    Supposedly, I put an object on a scale inside the elevator of a building, the scale reads m1. I start the elevator to the top of the building, during acceleration, the scale reads m2. As the elevator normalized, the scale reads m1. During the deceleration at the top, the scale reads m3. The entire ride lasted t seconds. I am asked to calculate the height of the building using this data.

    2. Relevant equations
    I am not sure if these are all the equations i need:

    v = (v0) + at
    x = (x0) + (v0)t + (1/2)a(t^2)
    (v^2) = (v0)^2 + 2a(x-(x0))

    3. The attempt at a solution
    I have calculated the height of the building using trigonometry by using a protractor to find the angle from a point on the ground to the top of the building. Using that angle and a distance d on the ground, I was able to find the height using tan θ = y/d .
    But I'm not sure how to use the scale data to get the height of the building.
  2. jcsd
  3. Nov 16, 2011 #2


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    Homework Helper

    Welcome to PF!
    I think you've got it with those equations plus good old d = vt (which applies for most of the ride). It will be tricky to do the accelerated motion at the beginning and end since you don't know their times. I would suggest assuming time t1 for the acceleration phase. Likely you will be able to calculate the deceleration time from that and the mass (weight?) measurements, from which the accelerations can be found. Who knows, maybe the t1 will disappear in the final answer.
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