What happens to mechanical energy when two materials rub against each other?

When two materials rub against each other, the mechanical energy involved primarily converts to heat energy through a process known as friction. This occurs because the microscopic roughness of the surfaces generates resistance as they come into contact, leading to energy loss in the form of heat. The warmer the surfaces become, the more the mechanical energy is transformed into heat energy.

This conversion is fundamental in understanding how energy transfer operates in various physical systems, particularly in fire dynamics where friction plays a significant role in increasing temperatures. Recognizing this transformation is important for firefighters when considering how materials heat up and potentially ignite during a fire situation. Understanding this can assist fire personnel in making tactical decisions based on the materials involved and their behavior under friction. The other options do not adequately describe this fundamental process resulting from friction.