Physics

Fontaine · #1 09-29-2008, 08:11 PM

If i have the coefficient of kinetic friction, how can i find the coefficient of friction?

for instance i have a number like this:

a block on a 20 degree angle, with a coefficient of kinetic friction of 0.58, how would i determine the coefficient of friction?

GassieBall · #2 09-29-2008, 08:16 PM

Boy, it's been 15 years since physics for me, but I always thought that the coefficients of friction (both static and kinetic) were determined experimentally. Therefore, you'd have to look them up (CRC Handbook of Physics). I don't think you have given enough variables to be able to solve for an unknown in an equation.

Frank Tuesday · #3 09-29-2008, 08:21 PM

You have the coefficient of kinetic friction. Are you looking for the coefficient of static friction? Are you looking for the frictional force?

The coefficient of static friction would have to be given. If you are looking for the frictional force, which is equal to your normal force * coefficient, sum your forces in the y direction.

N*cos(20)+f*sin(20)-mg = 0

f = N * mu

N*cos(20) + N*mu*sin(20) = mg

or

f*cos(20)/mu + f*sin(20) = mg

GassieBall · #4 09-29-2008, 08:27 PM

I agree that the OP is confusion. We're missing something. He's asking for the coefficient of friction but not specifying which one. Forget it. I'm not a physic major.

Fontaine · #5 09-29-2008, 09:05 PM

see im also missing data my group sent me that info and told me to get the "coefficient of friction"

i am also a bit confused because i thought i need the normal force (Fn)

Munjibunga · #6 09-30-2008, 12:08 AM

Multiply by the sine of the angle.

iamthebassplayr · #7 09-30-2008, 12:59 AM

Quote:

Originally Posted by Frank Tuesday

You have the coefficient of kinetic friction. Are you looking for the coefficient of static friction? Are you looking for the frictional force?

The coefficient of static friction would have to be given. If you are looking for the frictional force, which is equal to your normal force * coefficient, sum your forces in the y direction.

N*cos(20)+f*sin(20)-mg = 0

f = N * mu

N*cos(20) + N*mu*sin(20) = mg

or

f*cos(20)/mu + f*sin(20) = mg

+1, sum the forces in the Y and find Force of the ramp normal. What is the mass of the block?

Mike Money · #8 09-30-2008, 01:35 AM

What the hell are you talking about, Fontaine?