# Power Problem Pushing a Train

1. Jan 28, 2010

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. Jan 28, 2010

### PhanthomJay

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.

3. Jan 28, 2010

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?