# Pressure - Key terms

### ATMOSPHERE:

A measure of pressure, abbreviated "atm" and equal to the average pressure exerted by air at sea level. In English units, this is equal to 14.7 pounds per square inch, and in SI units to 101,300 pascals.

### BAROMETER:

An instrument form easuring atmospheric pressure.

### BUOYANCY:

The tendency of an objectimmersed in a fluid to float.

### FLUID:

Any substance, whether gas or liquid, that conforms to the shape of itscontainer.

### FLUID MECHANICS:

The study of the behavior of gases and liquids at rest and in motion.

### HYDROSTATIC PRESSURE:

the pressure that exists at any place in a body of fluid due to the weight of the fluid above.

### PASCAL:

The principle SI or metricunit of pressure, abbreviated "Pa" and equal to 1 N/m 2 .

### PASCAL'S PRINCIPLE:

A statement, formulated by French mathematician and physicist Blaise Pascal (1623-1662), which holds that the external pressure applied on a fluid is transmitted uniformly throughout the entire body of that fluid.

### PRESSURE:

The ratio of force to surface area, when force is applied in a direction perpendicular to that surface. The formula for pressure ( p ) is p = F / A , where F is force and A the surface area.