# Missed my class and don't know how to even begin.

1. Feb 13, 2012

### Dko

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

a 100kg bicycle and rider initially move at 16 m/s up a 15 degree hill. The rider slams on the brakes and skids to rest. The coefficient of friction is (0.8, 0.7)

2. Relevant equations
I have a few but nothing to do with a coefficient of friction.
The last ones given to me where like
MVi + ƩF(Δt) = MVf

3. The attempt at a solution
I can' make any since I was sick for class. I'm sure the professor was supposed to give at least a hand out with some explanation. So could someone at least give me a idea what I have to look up online that will help me get started on this problem?

2. Feb 13, 2012

### Scintillation

What exactly are you trying to solve for? I'm guessing time?

3. Feb 13, 2012

### Dko

Gehh sorry. Why do I keep forgetting that?
a. How far does the bike skid?
b. What was the elapsed time before the bike stops skidding?

4. Feb 13, 2012

### Biosyn

This is what I have to help so far.

(100kg)(16m/s) + ƩF(Δt) = 0

ƩF = (-mg sin(15) + uFn)
→ƩF = (-9.8 x 100kg x sin(15)) + u( 100 x 9.8 x cos 15)

→ƩF = -1232.877407

(100kg)(16m/s) + (-1232.877407)(Δt) = 0

1600 = (1232.877407)(Δt)

Δt = 2.59

I'm not sure if it is right, I might have forgotten a few things. Mainly...how to find ƩF

Please correct me! I'm only a freshman.

Last edited: Feb 13, 2012
5. Feb 13, 2012

### richukuttan

Hi,
The basics are, 2 forces act on the bike:-
Friction=Normal force * coefficient of KINETIC friction = (mg cosθ)*k
gravitational force=mg sinθ

From this info, find acceleration

use v2-u2 =2as to find distance
use v=u+at to find time.

I'm not sure there are no other factors. Pls check!!