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Homework Help: Question about (KINETIC ENERGY AND WORK)

  1. Apr 3, 2009 #1
    1. The problem statement, all variables and given/known data
    hi guys how are you?? ,, there are 2 MC (Multiple choices question)
    1- A 50-N force is the only force on a 2-kg object that starts from rest. When the force has been acting for 2 s the rate at which it is doing work is:(Ans:2500W)

    2-A 50-N force is the only force a 2-kg crate that starts from rest. At the instant the object has gone 2m the rate at which the force is doing work is:(Ans:500W)

    3. The attempt at a solution
    i tried several ways but the problem is i know only 2 equations about power
    one is P=W/t and P=Fv ,, in problem 1 there is no distance and in 2 there is no velocity, i didn't understand the questions in the first place(cant imagine it) ,, is the force acting horizontally or vertically ,, can anyone help me please before the exam,,
  2. jcsd
  3. Apr 3, 2009 #2
    For the first one, you can calculate the distance based on the information given. Note that the object is in something like freefall, since the 50N force is the only thing acting on it.
  4. Apr 3, 2009 #3
    thanks ,, first one solved :) ,, still with the second...
  5. Apr 3, 2009 #4


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    Just curious what the other multiple choices were.
  6. Apr 4, 2009 #5
    in 1)
    A. 75W
    B. 100W
    C. 1000W
    D. 2500W
    E. 5000W

    A. 2.5W
    B. 25W
    C. 75W
    D. 100W
    E. 500W
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