Constant velocity problem, where does increase in energy come from??? Let's say that an object is being pushed with a constant force across a surface, and it is moving with a constant velocity. We can use Newton's second law to show that the force of friction is equal to the force of the push. Considering the object only as the system: The work done by the push is W = Fpush*x The work done by the friction is W = -Ff*x If the force of the push is equal to the force of friction, the net work on the object would be 0. The object has no change in kinetic energy, no change in potential energy, but should have an increase in thermal energy from the friction that occurs. If there is no work, how did the total energy of the system increase? What am I missing here?