# Acceleration on an incline

1. Feb 24, 2004

### RingWraith2086

Question: The record for grass skiing was set blah blah blah. Suppose it took Spinka 6.60 s to reach his top speed after he started from rest down a slope with a 34 degree incline. If the coefficient of friction between the skis and the grass was 0.198, what was the magnitude of Spinka's net acceleration? What was his speed after 6.60 s?

Here's what I've done:
I thought a=g(sinTheta)
Which gives me
a = 9.81(sin34)
a = 5.486 m/s2,
which isn't right. What am I doing wrong?

2. Feb 24, 2004

### jamesrc

Don't forget the friction:

$$F_{\rm net} = ma = mg\sin\theta - \mu mg\cos\theta$$

Solve for a (you'll see that m cancels out) and then use kinematics to get the speed part.

3. Feb 24, 2004

### RingWraith2086

Well you just seem to know everything don't you? Maybe once I get through a quarter of physics I'll be able to help people too. Thanks once again.

4. Feb 24, 2004

### jamesrc

If only I did... Well, I'm glad I knew enough to help you here. It's also good to hear your willing to help when you can too. Keep up the good work.