# Homework Help: Kinetic and Static Friction

1. Nov 18, 2012

### michelle2011

1. The problem statement, all variables and given/known data
I am trying to start a project. My first step is to figure out the time a car fell off of a cliff. I know the height of the cliff which 40 meters, the base of the cliff from the car when it reaches the bottom which is 30 meters. The car has a static friction coeffiecient of 0.1 and a kinetic (sliding) friction coeffiecient of 0.50. Before it falls off the cliff it slides 2 meters and the car has a mass of 1000 kg.

2. Relevant equations
f(kinetic)=coffecient of kinetic friction x mass x gravity

3. The attempt at a solution
I tried to find the force by setting the above equation equal to kinetic friction which equals the force

2. Nov 18, 2012

### Spinnor

You wrote,

"The car has a static friction coeffiecient of 0.1 and a kinetic (sliding) friction coeffiecient of 0.50. "

The static friction coefficient should be larger?

The way you word your problem I have now idea what is going on. A picture might help or a better description of the problem.

3. Nov 19, 2012

### Basic_Physics

You should be able to get the speed with which the car left the cliff by assuming projectile motion. Working backwards one can then get the initial speed of the car before it started to skid.