1. The problem statement, all variables and given/known data A truck is moving at constant velocity v0 with a box of mass m on it. Suddenly it starts decelerating until its velocity becomes zero. Between the box and the truck the is a force of friction and the deceleration of the truck is sufficiently slow to allow the box not to start moving or rotating relative to the truck. What is the work done by all the forces applied to the box? 2. Relevant equations ΔK = W 3. The attempt at a solution It seems to me rather obvious that the work is simply W = ΔK = - 1/2 m v2 but my teacher said it is 0 and I really can't see why. Thanks in advance!