1. The problem statement, all variables and given/known data May i know how do i compute an energy conservative equation for the scenario below, which i don't understand. If a book is lifted up by a force in order to make it moving upward with a constant velocity. For conservation of total energy, W1-2 = U1-U2 = K2 - K1 If the object is moving in a constant velocity, isn't K2 - K1 = 0 However, U1 is not equal to U2. It seems not correct obviously, hope someone could enlighten me. I guess W1-2 = U1-U2 = K2 - K1 is only valid for isolated system, which should be a system without any external force involves except gravitational force. I'm very confuse now, hope someone could help me.