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