Question

One particular descent goes from 2100m to 1600m. Assuming work done against friction is 90% of the potential energy change of the cyclist and the cycle, what increase in speed in Km/h can a rider attain by the end of the
descent?

Answer 1

Answer:

1/2 M V^2 = .1 M g H       where 10% of PE goes into KE

V^2 = .2 g H = .2 * 9.8 * (2100 - 1600) = 980 m^2 / s^2

V = 31.1 m/s       increase in speed during descent

1 km / hr = 1000 m / 3600 sec = .278 m/s

V = 31.1 m/s / (.278 m/s / km /hr)= 112 km/hr