1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Finding the power of an elevator motor

  1. Feb 8, 2012 #1
    1. The problem statement, all variables and given/known data

    A 650kg elevator starts from rest. It moves upward for 3s with constant acceleration until it reaches its cruising speed of 1.75m/s.
    A) What is the average power of the elevator motor during this time period?
    B) How does this power compare with the motor power when the elevator is at its cruising speed?

    2. Relevant equations
    I think I did part a correctly, but I would like someone to check it. I don't really understand where to start with part b, how is it different than part a?


    3. The attempt at a solution
    Pavg = W/dT = (F*d)/t = ((ma+mg)*(v*t))/t = ((m(v/t)+mg)*(v*t))/t = (650kg(((1.75m/s)/3s) + 9.8m/s^2)*(1.75m/s*3s))/3s = 11811.04W
     
  2. jcsd
  3. Feb 8, 2012 #2

    Delphi51

    User Avatar
    Homework Helper

    Welcome to PF, Pete.
    All okay except the replacement of d with vt. That would be assuming the motion is at constant speed, which it is not. Use an accelerated motion formula to find d.
    The formula P = F*v will also work with the average velocity. Should be half your answer.
     
  4. Feb 8, 2012 #3
    Thanks. Do you have any idea on how to get started on part b?
     
  5. Feb 8, 2012 #4

    Delphi51

    User Avatar
    Homework Helper

    Same thing but leave out the ma term, which is zero.
    Velocity is steady on 1.75 now, so you could use d = vt.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Finding the power of an elevator motor
  1. Power of Elevator (Replies: 1)

  2. Elevator with Power (Replies: 3)

  3. Elevator Power (Replies: 2)

Loading...