a horse whose mass is gallops at constant speed up a long hill whose vertical height is , taking an amount of time to reach the top. the horse's hooves do not slip on the rocky ground, so the work done by the force of the ground on the hooves is zero (no displacement of the force). when the horse started running, its temperature rose quickly to a point at which from then on, heat transferred from the horse to the air keeps the horse's temperature constant.