Acceleration on an incline

  • #1
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?
 

Answers and Replies

  • #2
jamesrc
Science Advisor
Gold Member
476
1
Don't forget the friction:

[tex] F_{\rm net} = ma = mg\sin\theta - \mu mg\cos\theta [/tex]

Solve for a (you'll see that m cancels out) and then use kinematics to get the speed part.
 
  • #3
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
jamesrc
Science Advisor
Gold Member
476
1
Originally posted by 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.

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.
 

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