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.

\[P = \frac{F}{A}\]

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

\[= 2450Pa\]