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Power Problem Pushing a Train

  1. Jan 28, 2010 #1

    adk

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    1. The problem statement, all variables and given/known data

    What power is required to push a train weighing 110,000 kilograms up an incline of 1 in 100 at 20 kilometers per hour, all frictional resistances being neglected?

    2. Relevant equations
    P = ΔE/ ΔT


    3. The attempt at a solution

    This is the only power equation we discussed:
    P= ΔE/ ΔT = (m)(g)(h)/t
    This doesn't really fit with the data given b/c there's a velocity. Also
    I don't know how to express that ratio of 1 in 100 in the equation.
     
  2. jcsd
  3. Jan 28, 2010 #2

    PhanthomJay

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    Science Advisor
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    Gold Member

    the power required to push the train at constant speed may be determined from Power = Force times velocity, where the force is the pushing force which you can calculate from equilibrium considerations. Or you can calculate that force and use P= work/time, where work is the pushing force times the distance travelled in the direction of the force (letting h=1 m, find the distance travelled up the incline to reach the 1 m high mark using the 1:100 slope), then you can calculate the time it takes for the train to reach a point 1 m high using kinematics. Or else use your listed equation, finding t in the same manner...it all leads to the same answer.
     
  4. Jan 28, 2010 #3

    adk

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    If we use the first equation:

    F=m*a = (110,000)(9.81) = 1079100
    P=1079100*20km/hr=21582000 N

    Is this correct? Where do you go from here?
     
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