1. The problem statement, all variables and given/known data 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? 2. Relevant equations My answer: d = (vf2 + vi2) / 2a 3. 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?