# Friction and angles

1. Nov 19, 2014

### Thegiver431

how do you find friction force when applied force is at an angle, this is on a flat horizontal surface.

2. Nov 19, 2014

### Staff: Mentor

Usually you will need to break at least one force into components.

3. Nov 20, 2014

### Maged Saeed

the static frictional force is :

$$u_sF_n$$

[Us] is constant and [F_n] is the wieght of the object the force is applied to plus the vertical component of the force ,, I think :)

Remember that the frictional force is always in opposite direction of the applied force , that means they would have a different signs

Last edited: Nov 20, 2014
4. Nov 20, 2014

### CWatters

Fn is the force normal to the surface (it need not be the "weight" of the object or even "vertical").

In these two examples the normal force is the weight of the object modified by the vertical component of the applied force F.
http://philschatz.com/physics-book/resources/Figure_06_01_07a.jpg

in a) that would be

Fn = mg+FSin(25)

in b) that would be

Fn = mg-FSin(25)

Since friction is proportional to Fn that means b is easier than a)