Definition of Pressure

“Thrust per unit area” OR “Force acting on an unit area of surface”.

Definition of Pressure

More About Pressure:

  • Thrust is the perpendicular force acting on a body.
  • Pressure is the ratio of Force to the Area over which that force is distributed.
  • The S.I. unit of Pressure is the “PASCAL”
  • Pressure is a scalar quantity, it has no direction.
  • When the area is small, a moderate force can create a very large pressure. This is why a sharp knife is good at cutting things: when you push the very small area of the sharp blade against something, it creates a really large pressure.

Examples of Pressure:

  • The studs on a foot ball boot have only a small area of contact with the ground. The pressure under the studs is high enough for them to sink into the ground, which gives extra grip.
  • The area under the edge of a knife’s blade is extremely small. Beneath it, the pressure is high enough for the blade to push easily through the material.
  • Tractors that have to work on soft ground are fitted with wide tyres. Larger area of tyres reduces the pressure and will not sink into ground.

Solved Example on Pressure

A small table weighing 40N stands on four legs, each is having an area of 0.001m2. What is the pressure of the table on the floor?
    A. 400N/m2
    B. 1000N/m2
    C. 10 000N/m2
    D. 40 000N/m2

    Correct Answer is D.


    Step 1: Write down the formula for pressure p = F/A
    Step 2: Area = Area of 4 legs of table = 4 x 0.001 = 0.004m2
    Step 3: Force = 40 N
    Step 4: Applying the known values in the formula p = 40 / 0.004 = 40 000N/m2

Related Terms: Liquid pressure | Atmospheric pressure | Pascal’s law | Boyle’s law | Bernoulli’s principle.