Okay, so this is a homework problem, just so that everybody knows it.

A train with the mass m=260 metric tons accelerates (from velocity=0) along horizontal, straight rail tracks. The moment the velocity is 36 km/h the power is 650 kW. The resistance against the movement is 0,5 % of the weight of the train.

a)Find the force with which the engine pulls the train forwards and the acceleration when the velocity is 36 km/h.

b)How does the acceleration change if the power of the engine is the same for a while (the acceleration after the one we calculated in a))?

Ok, so my physics teacher says that P=W/t. To this point I agree.

Furthermore he says that W=F*d (d is the distance) and thus P=F*d/t=F*v, and I don't agree. To says that W=F*d, the force must be constant, which it isn't.

So I reckon I'm right and I don't know how I should solve it. Any suggestions?

:-D