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Homework Help: Elevator problem: energy, power, intensity,

  1. Apr 21, 2009 #1
    1. The problem statement, all variables and given/known data
    Question: An Elevator and its load have a mass of 1200 kg.
    a) what energy must be supplied to lif the elevator and its load ot a height of 100m? Answer: E = _________ Joules

    b)If the elevator rises at a speed of 5 m/s, how long does it take to cover 100m? Answer t= __________ sec

    c) What is the power supplied? Answer P = ________ Watts

    2. Relevant equations
    Energy: E=MgL, where g=9.8m/s2 (squared) is the acceleration of gravity and Lis the distance through which a mass is moved against the force of gravity
    Power: P = E/t
    Intensity: I= P/A

    3. The attempt at a solution

    My answers:
    For part a, I used the first equation (E=MgL) and I got the answer of 1176 Joules

    part b: at a rate of 5 m/s it would take 20 seconds; so t = 20 seconds

    Part c: P=E/t is P= 1176/20 = 58.5 watts

    Does this seem right?
  2. jcsd
  3. Apr 21, 2009 #2


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    Homework Helper
    Gold Member

    The answer to the first one should be 1176000 Joules, but your formulas are correct.
  4. Apr 21, 2009 #3
    Thank you for taking time to help!!! I appreciate it!
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