How Does Doubling Speed Affect Energy Use Against Drag in Cycling?

[justunme]

In this problem assume that all of the energy expended goes into working against drag. Assume that F is proportional to v-squared exactly & that the air is motionless with respect to the ground. Suppose a cyclist and the bicycle have a combined mass of 60kg and is moving a 5m/s.

A) If the drag force on the cyclist is 10N, how much energy does the cyclist use in traveling 1 km?

B) If speed is doubled to 10 m/s, how much energy is used in traveling 1 km?

C) Upon slowing down to 5 m/s, we hit a head wind of 5 m/s, How much power is being expended?

2. Homework Equations

W = Fd

P = W/change in time3. The Attempt at a Solution

A) W = 10N x 1km = 10 kj

B) ?

C) ?

 

[kuruman]

Hi justunme and welcome to PF. For part (B), if the speed is doubled does the drag force change? If so, by what factor?