Figure out how far up the incline of the hill the box slides.

  • Thread starter jumbogala
  • Start date
  • #1
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Homework Statement


At the bottom of a hill, a box has a speed of 15 m/s. The hill forms an angle of 30 degrees with the horizontal. How far up the incline of the hill does the box slide?


Homework Equations


My answer:
d = (vf2 + vi2) / 2a

The Attempt at a Solution


vi = 15 m/s
vf = 0 m/s

a = (-9.81 m/s2)*cos(30) = -8.49 m/s2

d = 13.25 m

However, the answer key says d = 23 m. This is the answer if you use a = (9.81 m/s^2)*sin(30) instead. Help?
 

Answers and Replies

  • #2
Doc Al
Mentor
45,030
1,329
What's the component of gravity acting down the incline? That's where sinθ comes in.
 
  • #3
423
2
Oops, I had 30 degrees in the wrong corner of the triangle. It works now! Thanks.
 

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