1. The problem statement, all variables and given/known data A fork-lift truck lifts a crate of machinery parts of mass 600kg from the floor of a warehouse and transports it at a steady speed of 1.5m/s on to the back of a semi-trailer that is 1.5m above the ground. What happens to the kinetic energy of the crate when the fork-lift stops? 2. Relevant equations none 3. The attempt at a solution Energy must be conserved. I like to say that the kinetic energy it gained was supplied by the truck which it obtained from the burning of fuel. When the fuel stops burning, energy in the system is reduced and one type of energy that will vanish when the fuel stops burning is kinetic energy of the fork-lift. So to answer the question, when the fork-lift stops, the kinetic energy of the crate has gone because fuel energy is gone. But does that dosen't sound too right does it? Although I can't see anything wrong with it.