(adsbygoogle = window.adsbygoogle || []).push({}); [SOLVED] Friction Problem

1. The problem statement, all variables and given/known data

A bicyclist can coast down a 5° hill at a constant 8.0 km/h. Assume the force of friction (air resistance) is proportional to the speed v so that Ffr = cv.

(a) Calculate the value of the constant c.

________ kg/s

(b) What is the average force that must be applied in order to descend the hill at 18 km/h? The mass of the cyclist plus bicycle is 85 kg.

________N

2. Relevant equations

Sigma F = ma

Ffr = cv

3. The attempt at a solution

First i converted my 8 km/hr into 2.22 m/s. Then i went into the parallel forces which are Ff and Fwx. The sum of their forces is equal to 0 because its acceleration is 0 so Ff is equal to Fwx and Fwx is equal to sin5 times mg which equlaed .854m. Then i set that equal to 2.22c because Ff also equal that. Now I'm stuck because I don't have mass. I tried writing out all units and canceling out so that on kg/s was left, but that didn't work out.

Any ideas?

**Physics Forums - The Fusion of Science and Community**

# Friction Problem

Know someone interested in this topic? Share a link to this question via email,
Google+,
Twitter, or
Facebook

Have something to add?

- Similar discussions for: Friction Problem

Loading...

**Physics Forums - The Fusion of Science and Community**