1. The problem statement, all variables and given/known data A sled starts from rest and slides down an inclined plane with constant acceleration. In three seconds, it has travelled 9m. How long does it take to reach a velocity of 24m / s? 2. Relevant equations d = vi * t + ½ * a * t^2, vi = 0 vf = vi + a * t, vi = 0 3. The attempt at a solution d = vi * t + ½ * a * t^2, vi = 0 9 = ½ * a * 3^2 a = 18 ÷ 9 = 2 m/s^2 To determine the time, we need to determine the sled’s acceleration. vf = vi + a * t, vi = 0 24 = 2 * t t = 12 seconds. I solved this problem with help of someone else . The thing I don't understand is why can't we use 9,81 m/s2 for acceleration . Because the sled is sliding down . Doesn't it has to do with gravity ?