A 4 kg bundle starts up a 30° incline with 128 J of kinetic energy. How far will it slide up the plane if the coefficient of friction is 0.30? So the solution to the problem is 128 = 4(9.8)(x)(sin30) + 0.30 (4)(9.8)(x)(cos30)....x = 4.29m I dont understand the solution. so 128 = 4(9.8)(x)(sin30) + 0.30 (4)(9.8)(x)(cos30) is KE = mgh (sin theta) + Friction (mgh)(cos theta) I thought it would be KE = PE + Friction, why is mgh added twice???