A mechanical explosion is primarily caused by a buildup of what?

A mechanical explosion is primarily caused by a buildup of heat and pressure. In many scenarios, such as in boilers or pressure vessels, the failure to release heat effectively can lead to increased pressure within the system. This pressure continues to build until the structural integrity of the containment is compromised, resulting in an explosion.

For instance, when gases are heated, they expand, increasing the pressure in a confined space. If that pressure surpasses the material's ability to contain it, an explosive failure occurs. Thus, understanding the dynamics of heat transfer and pressure management is crucial in environments where mechanical systems operate under stress.

The other options do not adequately address the fundamental causes of mechanical explosions. While gas and liquid can be involved in various explosive scenarios, they do not encompass the necessary combination of heat and pressure that leads to a mechanical explosion in confined systems. Similarly, heat and light, as well as pressure and sound, do not directly pertain to the essential physical mechanics that result in such explosions.