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!

Power Problem Pushing a Train

  1. Jan 28, 2010 #1


    User Avatar

    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


    User Avatar
    Science Advisor
    Homework Helper
    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


    User Avatar

    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?
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Similar Discussions: Power Problem Pushing a Train
  1. Train problem (Replies: 2)

  2. Train Problem (Replies: 3)