Firefighters just finished eating dinner when a working fire came in. On the fireground the food energy expended to raise a ladder is balanced by the mechanical movement of the ladder and the firefighter pulling the halyard rope, minus the energy needed to overcome wind resistance, imperfect pulley, and ladder pawls, as well as the energy dissipated by perspiration and stimulated breathing. This is an example of of the _________
- Law of physical energy
- Law of perpetual motion
- Law of conservation of energy
- Law of thermodynamics