Pressure

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.

Pressure can be determined using the following equation.

Pressure = \frac{{force}}{{area}}

P = \frac{F}{A}

  • The unit for pressure is the pascal ( Pa).
  • One pascal is equivalent to one newton per square metre.
  • Atmospheric pressure is approximately 1\times 10^{5} Pa = 100000 Pa.
Question

A cube-shaped box of mass 10kg is sitting on a level table. If the length of each edge of the box is 0.2m, calculate the pressure the box exerts on the table.

Step 1

First calculate the weight of the box.

Weight\,\,of\,
\,box=mass\left ( m \right )\times\,gravitational\,\,field\,\,strength\left ( g \right )

Mass = 10

Gravity = 9.8

mg = 10 \times 9.8 = 98N

Step 2

Then calculate the area of the box in contact with the table.

Area of box in contact with table

= 0.2 \times 0.2 = 0.04{m^2}

Step 3

Now calculate the pressure.

P = \frac{F}{A}

P = \frac{{98}}{{0.04}}

= 2450Pa