# Homework Help: What is the coefficient of friction?

1. Oct 10, 2011

### g65hy

An object on a 30 degree inclined surface with force applied up the ramp,
weight of object = 6.9N,
applied force on object = 3.13N

My answer was -0.05, but I'm not sure if this is right so I want to make sure with someone's help

Thanks

2. Oct 10, 2011

### SammyS

Staff Emeritus
I'm not sure either. Is there a complete question here?

What's the complete statement of the problem?

3. Oct 10, 2011

### g65hy

yes the information is complete, I had to take it from a table with info in it so theres no complete statement, and btw theres no acceleration

4. Oct 10, 2011

### SammyS

Staff Emeritus
So, these are observed data?

There's no way to know the coefficient of friction, without more information.

You can determine the frictional force -- perhaps -- but not the coefficient .

5. Oct 10, 2011

### g65hy

Ive done it for every other question...but im in grade 11 and our formula for the coefficient of friction is μ=Ff/Fn

If you don't think theres enough info, could you do just the friction? Thanks

6. Oct 10, 2011

### SammyS

Staff Emeritus
That's IF either of the following is true as well as the direction of the applied force is known.

1. The object is moving at a constant speed. (kinetic friction)

2. The object is stationary, but just on the verge of moving. (static friction.)

7. Oct 10, 2011

### g65hy

1. yes
2. yes

Im only in gr 11 physics so it wont be very complicated

8. Oct 10, 2011

### g65hy

The object is on a high friction surface (sand paper) and is just on the verge of moving at a constant velocity

9. Oct 10, 2011

### DukeLuke

Negative coefficients of friction do not conserve energy. If you want more help you should post more work.

edit: forgot to hit "post" and didn't see previous help

10. Oct 10, 2011

### g65hy

I got negative because since this was a lab, we tried to make the slope 30 degrees but probably wasnt
Thats why my teach says we may get a negative answer

11. Oct 10, 2011

### g65hy

So could anyone work out either the coefficient of friction or just friction?