16.1  Thermal Energy and Matter (continued)

Work and Heat

A drill is a machine that does work on the cannon. Remember that no machine is 100 percent efficient. Some of the work done by the drill does useful work, but some energy is lost due to friction. Friction causes the moving parts to heat up. The more work done by the drill, the more that friction causes the cannon to heat up.

Heat is the transfer of thermal energy from one object to another because of a temperature difference.   Heat flows spontaneously from hot objects to cold objects. Heat flows from the cannon to the water because the cannon is at a higher temperature than the water.