Question 16
a) Power = Work done divide by time
Power = mgh/t= 3.92 kW
b) Power = mgh/t= mgv = 196W
Note : h/t is height per sec which is velocity!
Question 17
a) Motorcycle at steady speed means no net force , hence F motor = Fr
P = Fm(v)= 4.0 kW
b) P = Fm (v) but Fm = Fr + mgsin37 = 1676 N
P = 33.5 kW
c) Redraw force diagram , motorcycle travelling down!
Fm + mgsin37 + Fr
Fm = Fr - mgsin37 = -1276 N
P = - 25.5 kW
Note: This negative power means that the motorcyclist must be applying the brakes instead of his accelerator!
