An engine is hauling a train of mass `m` on a level track at a constant speed `v`. The resistance due to friction is `f`. What power is the engine producing? What extra power must the engine develop to maintain the speed up a gradient 1 in l. What is the new total power developed by the engine develop to maintain the speed up a gradient 1 in l. What is the new total power developed by the engine ?
A. Power expended by the engine is "mfu".
B. The extra power developed by the engine to maintain a speed `u` up a gradient on of `h` in `s` is `(mghu)/(s)`.
C. The frictional force exerting on the train is `mf` on the level track
D. None of above is correct
