Definition Of Pressure
"Thrust per unit area" OR "Force acting on an unit area of surface".
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.
Solution
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.