What are the units of pressure in the SI system?

The units of pressure in the SI (International System of Units) are Pascals. A Pascal is defined as one newton of force applied over an area of one square meter. This unit is fundamental in measuring pressure and is widely used in various scientific and engineering contexts.

In more detail, pressure is the measure of force exerted perpendicular to the surface of an object per unit area, and the Pascal provides a straightforward way to quantify this force-area relationship. Because 1 Pascal equals 1 Newton per square meter, it effectively encapsulates how much force acts on a given area, which is essential for understanding phenomena involving fluid dynamics, structural integrity, and material science.

Other options, though they represent measures of pressure, are not part of the SI system. For instance, atmospheres and bars are commonly used units of pressure in various applications but are not classified as SI units. Newtons per square meter is technically equivalent to Pascals; however, the standardized unit used in practice for pressure measurement is specifically the Pascal, making it the correct answer in this context.