How is static pressure defined?

Static pressure is defined as the pressure exerted by a fluid at rest. This definition captures the essential characteristic of static pressure, which measures the force per unit area applied in all directions by the fluid when it is not in motion. In the context of fluid mechanics and aerodynamics, understanding static pressure is crucial, as it helps determine how fluids behave when they are stationary and serves as a baseline for measuring other pressures, such as dynamic pressure, which is associated with fluid in motion. Recognizing static pressure is fundamental in various applications, including aircraft performance, where it influences lift and drag characteristics.

The other options address relevant concepts but do not accurately define static pressure. For example, the pressure from a fluid in motion describes dynamic pressure, while the combined pressure of static and dynamic forces refers to total pressure, which includes both components. Atmospheric pressure at ground level is a specific instance of static pressure but does not encompass the general definition applicable in various fluid contexts.