# Homework Help: Force of Friction Equation?

1. Jan 26, 2004

### paigegail

I think the reason that my problems have arisen is because of my equation for the force of friction. I have

Ff= ucosAngle

That right?

2. Jan 26, 2004

### chroot

Staff Emeritus
The force due to friction:

$$F = \mu N = \mu m g$$

Where $\mu$ is the coefficient of friction (either static of kinetic), and $N$ is the normal force. On a horizontal plane, the normal force is just the weight of the object, which is $mg$.

- Warren

3. Jan 29, 2004

### kishtik

And to include the angle;
$$F_f=\mu mg cos \alpha$$

4. Jan 29, 2004

### himanshu121

It is the limiting force of friction or say max friction force exerted and f force due to friction depends on the circumstance

For eg moving on a plane surface Chroots Ans is correct and in case if body is on inclined surface Kishtiks Ans is correct

5. Jan 30, 2004

### kishtik

I love my equation. What is the angle for a plane surface? 0? Then what is cos0? 1? Then what is 1.mu mg? mu mg? Are the two eqs the same?

6. Jan 30, 2004

### PrudensOptimus

lol rofl same eq man.

7. Jan 30, 2004

### himanshu121

It is not same equation

It is the case of the equation under the given conditions only