# Homework Help: Minimum distance in which the car will stop?

1. Sep 27, 2010

### hm8

1. The problem statement, all variables and given/known data
A car is traveling at 51.0 mi/h on a horizontal highway.
If the coefficient of static friction between road and tires on a rainy day is 0.100, what is the minimum distance in which the car will stop?

2. Relevant equations
$$\Sigma \vec{F} = m \vec{a}$$

$$v^2 = v_0^2 + 2 a \Delta x$$

$$f_s \leq \mu_s N$$

3. The attempt at a solution
Is it possible to do this problem without mass? Or did my teacher just forget to give us the mass?

If I had the mass of the car, I'd use it to find the normal force, and then plug that into the friction equation to find the force of friction...and then plug that into Newtons 2nd to find acceleration, and then use kinematics to find distance.

I suppose the minimum distance would be 0 if the car's mass was infinite but...I don't think that's what he's looking for.

2. Sep 27, 2010

### fizzynoob

Re: Friction

masses should drop out at the very end. Are you allowed to use conservation of energy? If you can than its just as simple as knowing the work done by the road and brakes