What form of energy is produced by engine combustion?

The correct choice, heat, is produced by engine combustion because combustion is a chemical reaction that occurs when fuel burns in the presence of oxygen, releasing energy. This reaction generates a significant amount of thermal energy, which is the heat produced during the process. In internal combustion engines, this heat energy is crucial as it is used to increase the temperature and pressure of gases inside the engine cylinders, ultimately converting that energy into mechanical power to move the vehicle.

While motion is a subsequent result of energy conversion in the engine, it does not directly relate to the energy produced during combustion itself. Friction is a force that occurs between surfaces in contact and does not represent energy generated by combustion. Traction refers to the grip or adhesion between the tires and the road, which is necessary for motion but is not a direct output of the combustion process. Understanding that combustion primarily produces heat helps to clarify the role of thermal energy in engine operation and performance.