A bus is travelling at a constant speed of 6.2ms-1 along a section of road that is inclined at an angle of 6.0degrees to the horizontal.
a) the total output power of the engine of the bus is 70kW and the efficiency of the engine is 35%. calculate the power to the engine
b) the mass of the bus is 8.5 x 10^3. determine the rate of increase of GPE of the bus
c) using your answer to b and the data in a, estimate the magnitude of the resistive forces acting on the bus
d) determine the magnitude of the net force opposing the motion of the bus at the instant at which the engine stops
e) discuss, with reference to the air resistance, the change in the net force as the bus slows down
2. The attempt at a solution
a) 70 000 / 0.35 = 200 000W
b) vertical distance: 6.2sin6 = 0.648
8.5 * 10^3 * 9.81 * 0.648 = 54 033 Js-1
c) 70 000 - 54 033 = 15967
15967/6.2 = 2575.3N
is this right ???
d) some suggestions would be useful for this one!
e) does the air resistance decrease proportionally to equal the thrust so that the net force decreases too?