# Help with friction

1. Feb 18, 2005

### FocusedWolf

Ok, before i start i'd like to say i'm totally confussed about how to use use the friction formulas in my book...i say this because all my answers are wrong!

Ok so what i need is help in the form of examples...and alot...cause my book doesn't offer anything.

Anyhoo, heres's a problem i'm trying to solve: ( i rounded off the numbers for clarity)

A block is at rest on an incline 30 degrees.

weight 10kg
Us .50
Uk .40

What is the frictional forces acting on the the 10kg mass. Answer in units of N

Someone help clarify a plan of attack...in meantime im gonna try reading this chapter some more.

2. Feb 19, 2005

### Andrew Mason

First find the normal force. In this case it is equal and opposite to the component of gravity that is perpendicular to the surface of the inclined plane. That will enable you to find the possible kinetic and static friction forces.

Then find the component of gravity along the surface of the inclined plane. That will tell you whether the block moves.

From that you can answer the question.

AM