# Homework Help: Finding minimum distance to stop using friction and velocity

1. Oct 5, 2011

### trivk96

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

A car is traveling at 44.4 mi/h on a horizontal
highway.
The acceleration of gravity is 9.8 m/s2
.
If the coeﬃcient of friction between road
and tires on a rainy day is 0.13, what is the
minimum distance in which the car will stop?
(1 mi = 1.609)

2. Relevant equations
x=xo+vot + at2
Ff=μ*Fn

3. The attempt at a solution

I honestly have no idea

Last edited: Oct 5, 2011
2. Oct 5, 2011

### Rayquesto

I'd use the kinetic energy work theorem. You learn that yet?

3. Oct 5, 2011

### Rayquesto

or you could use basic kinematic equations to solve this.

4. Oct 5, 2011

### trivk96

Haven't learned kinetic energy work theorems. Could you help me through the easier process. I have a test tomorrow and I want to understand this.

5. Oct 5, 2011

### Rayquesto

adding kinetic energy theorem to the problem basically takes into account mass while kinematic equations still hold true. I'd rather go into the kinematic equation realm. Basically, this is asking you what the acceleration of the car is and what distance the car travels if an initial velocity is 44.4mi/h. Convert that to meters/second.

6. Oct 5, 2011

### Rayquesto

and if you are ready for the test, then you'll use V^2=V0^2 + 2ax to get the x I mean the right answer.

7. Oct 5, 2011

### iRaid

$D=\frac{v_{o}^{2}}{2μg}$

I believe that is the equation.

8. Oct 5, 2011

### Rayquesto

i raid is correct!