- #1

Renton

- 2

- 0

## Homework Statement

Hi all,

I race bikes in my spare time and someone asked this on a cycling forum:

How much time could you save on a 40km race on a flat course, riding at 40km/h if your bike was one pound lighter. Let's say the weight of the rider and bike together is 80kg.

There was a time when I was younger when this would be trivial but right now I can't figure it out.

## Homework Equations

v = d / t

a = v - v0 / t

F = m * a

## The Attempt at a Solution

So I know I have to figure out how much time it takes to do the course in both cases.

And I know I have to factor in mass somehow.

t = (v-v0)/a = (v - v0) *m / F

And this is where I get stuck. I don't know what force is required to move the bike.

Thank you in advance and sorry about my English, it's not my first language :)