Pressure
Pressure is the force per unit area.
This means that the pressure a solid object exerts on another solid surface is its weightThe force acting on an object due to the pull of gravity from a massive object like a planet. The force acts towards the centre of the planet and is measured in newtons (N). 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 massThe amount of matter an object contains. Mass is measured in kilograms (kg) or grams (g). \(10kg\) 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.
\(P = \frac{F}{A}\)
\(P = \frac{{98}}{{0.04}}\)
\(= 2450Pa\)