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Power developed

  1. Dec 5, 2009 #1
    A jet engine develops 1 * 10^5 n of thrust in moving the airplane forward at a speed of 900 km/h. What is the power developed by the engine?

    I thought I needed to convert 900 km/h to m/s, so I did and I got 15000 m/s.

    The only equation I see to use for this is:

    P = Fvcosθ

    When I used the equation, I got:

    P = Fv
    = (1*105)(15000 m/s)
    = 1.5 * 109

    I know I went wrong somewhere because it is multiple choice and that wasn't any of the answers. Please help me see my error(s) and help me get it right. I need this done a.s.a.p. by tomorrow. Thanks.
  2. jcsd
  3. Dec 5, 2009 #2
    How many seconds are there in one hour?
  4. Dec 5, 2009 #3
    900km/hr= 900000m/s divide by 3600 sec/hr and you get what?
    Edit: sorry rootx, missed your response.
  5. Dec 5, 2009 #4
    My mistake. I completely missed that.

    900000 m/h /3600 s = 250 m/s

    And then I multiply that by the thing I had before:

    P = Fv
    = (1 * 105 N)(250 m/s)
    = 250000 W
    = 25 MW

    Thanks guys. I got too much going on in my mind right now. :redface:
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