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Homework Help: GPE Question

  1. Nov 22, 2004 #1
    Hey just gettin a bit stuck on this question.....i'll attempt to answer it, but it really doesn't look right to me.

    A cable car is used to carry people up a mountain. The mass of the car is 2000kg and it carries 80 people, of average mass 60kg. The vertical height travelled is 900m and the time taken is 5 minutes.

    i) Calculate the gain in GPE of the 80 people in the car

    GPE = mg/\ h

    = (80 x 60) x 9.81 x 900

    = 4.2 x 10^7 J

    Is this right so far? :confused:

    ii) Calculate the minimum power required by a motor to lift the cable car and its passengers to the top of the mountain.

    Power = Work Done/Time Taken

    Work Done = Force x Distance = (4800 + 2000) x 9.81 x 900
    = 6.0 x 10^7

    Power = (6.0 x 10^7) / 300 (as 5 mins = 300s)

    P = 2.0 X 10^5 watts

    These are the answers I got........i think i've used the right method, just need some reassurance!

    Thanx in advance!
  2. jcsd
  3. Nov 23, 2004 #2
    Working looks ok to me.
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