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?
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?