Initially, the tire has kinetic energy and potential energy. If we assume 0 potential energy at 7.9 m, then the initial energy is
E = mgh + ½mv² = 8.7kg * 9.8m/s² * (27.6 – 7.9)m + ½ * 8.7kg * (2.37m/s)² = 1,690 J
With on no account of energy loss, this will be the energy at the topmost of the 7.9m hill, which we distinct as having 0 potential energy. Then:
E = 1690 J = ½mv² = ½ * 8.7kg * v² v = 41 m/s
