A 8.63 kg box slides down a long, frictionless incline of angle 20 degrees. It starts from rest at time t = 0 at the top of the incline a height 24.6 m above ground. Find the potential and kinetic energy of the box at t = 1.8s. Answer in units of J. acceleration is gsin20 so I got velocity by gsin20 x 1.8 seconds and then I used .5mv^2 to find KE and then for PE I found PE at the highest point which is mgh and then subtracted KE from that I got 1925.2569 J for PE and 157.3863974J for KE (ignore sig figs) I entered this into UTexas and got it wrong. Please help.