Pressure is the force per unit area.
This means that the pressure a solid object exerts on another solid surface is its weight in newtons divided by its area in square metres.
p is the unit of pressure in pascals. One pascal is 1 N/m2
f is the unit of force in newtons
a is the unit of area in m2
Area is calculated by the following equation:
area = length × width
The units of length and width are metres.
A force of 20 N acts over an area of 2 m2. What is the pressure?
force ÷ area = pressure
20 ÷ 2 = 10 N/m2
To increase pressure - increase the force or reduce the area the force acts on. To cut up your dinner you can either press harder on your knife or use a sharper one (sharper knives have less surface area on the cutting edge of the blade).
To reduce pressure - decrease the force or increase the area the force acts on. If you were standing on a frozen lake and the ice started to crack you could lie down to increase the area in contact with the ice. The same force (your weight) would apply, spread over a larger area, so the pressure would reduce. Snow shoes work in the same way.