# Finding Friction Coefficient

1. Mar 7, 2006

### superdave

Here it is.
A 10 kg suitcase is placed on a flat ramp inclined at 37 deg. When released from rest, the suitcase accelerates down the ramp at .15 m/s^2. What is the coefficient of the kinetic friction between the suitcase and the ramp?

Now, from this I got Fnet=m*a=1.5 N in the x direction.

Fnet=Fx-kinetic friction=mg(sin theta)-mg(cos theta)(mu k)
solving for mu k:
mu k=mg(sin theta)-Fnet)/mg(cos theta)

Doing all the math gets me something like .46, but the back of the book disagrees. What am I doing wrong?

2. Mar 7, 2006

### vaishakh

The question is wrong. The acceleration is greater than g.

3. Mar 7, 2006

### superdave

It's 0.15 m/s^2. I left out the 0, so it might've looked like 15. Sorry.

4. Mar 7, 2006

### Hootenanny

Staff Emeritus
I can't see that you've done anything wrong.

5. Mar 7, 2006

### superdave

The answer I get is .468, but the book gives .73. Unless the book is wrong, which I guess is conceivable.

6. Mar 7, 2006

### Staff: Mentor

I set it up the same way and got u=0.734. Maybe just re-check your math after the last equation.

7. Mar 7, 2006

8. Mar 8, 2006

### superdave

Thanks, I got it. I had forgotten to add a parenthesis when putting it into my calculator. Stupid me. I tried to post this yesterday, but the forum seemed to go down.

9. Mar 8, 2006

### Hootenanny

Staff Emeritus
Yeah it did go down. Most errors I make are computational rather than systematic.