In basic mechanics, what is pressure defined as?

Pressure is defined as force applied per unit area. This definition is fundamental in mechanics and is crucial for understanding how force impacts surfaces. When a force is distributed over a specific area, the resulting pressure can vary depending on the magnitude of the force and the size of the area over which it is applied.

In practical applications, the concept of pressure is used in various fields, including fluid mechanics, engineering, and even atmospheric science. For example, the pressure in a tire can be understood by the force of the air inside the tire acting on its walls divided by the area of contact with the tire surface. This relationship helps to predict how changes in air volume or temperature can affect tire performance and safety.

The other definitions provided do not align with the concept of pressure. While mass times acceleration relates to force (Newton's second law), it does not describe pressure directly. Volume over mass gives density, and heat per unit volume relates to thermodynamic processes, which also does not pertain to pressure. Consequently, the definition that aligns accurately with the concept of pressure is indeed force per unit area.