What is the standard unit of pressure in the SI system?

The standard unit of pressure in the SI (International System of Units) system is the Pascal (Pa). One Pascal is defined as one newton per square meter, which means it measures the force applied over an area. This unit is widely used in scientific and engineering contexts due to its base derived from other SI units, specifically involving mass (kilogram), length (meter), and time (second).

While other units of pressure, such as atmosphere (atm) and bar, are also commonly used in various fields, they are not the standardized unit recognized by the SI system. Atmospheres and bars can be converted into pascals, indicating their relation but distinct definitions. The newton, although a fundamental unit representing force, is not a direct measurement of pressure without consideration of the area over which the force is applied. Thus, the Pascal is the most appropriate answer, as it directly defines pressure as a derived quantity in the SI framework.