What is a pressure?
The pressure acting on a surface is defined as the perpendicular force per unit area of surface.
The unit of pressure is the pascal, Pa, where 1 pascal is =1 newton per square metre. Thus pressure,
p = F/A pascals
where F is the force in newtons acting at right angles to
a surface of area A square metres.
When a force of 20 N acts uniformly over, and per-
pendicular to, an area of 4 m2, then the pressure on the
area, p, is given by:
p = 20 N/4m^2
= 5 Pa
