# Homework Help: Static Friction Text Problem

1. Feb 27, 2006

### Havoc2020

Hi, the problem I have is one dealing with static friction. The problem states: The coefficient of static friction between hard rubber and normal street pavement is about 0.8. On how steep a hill (maximum angle) can you leave a parked car?

I know that the downward force is "g" and that the normal force is equal to "g" since there is no acceleration. I am just having problems finding the angle. Our textbook is lacking in examples. I am not looking for an answer but a formula to use or even a hint.

2. Feb 27, 2006

### Astronuc

Staff Emeritus
On a flat horizontal surface, the weight (mg) would point directly down. As the angle increases, the weight points down, but the component normal to the surface is reduced by the cos of the angle.

See - http://hyperphysics.phy-astr.gsu.edu/hbase/frict2.html#fp
Look at the third pane.

Last edited: Feb 27, 2006
3. Feb 27, 2006

### Havoc2020

Thanks

Thanks for the help. The formulas and the diagram helped alot.

4. May 1, 2006

### dxsd

Which textbook did you get that question from? can give me the ISBN # and the site you bought it from ?

thanks