Pressure: Understanding Force on Surfaces For Class 8

Pressure is a physical quantity that tells us how force is distributed over a given area. Have you ever wondered why a nail with a sharp end is easier to hammer into a table than a flat-ended nail, even if you apply the same force? This happens because of pressure. It explains why some surfaces penetrate or resist forces differently. 

In this article, we will understand what is pressure and learn how to calculate it using some numerical examples.

Table of Contents

• Understanding What Pressure Is
• Examples and Numericals on Pressure
• Factors Affecting Pressure

Understanding What Pressure Is 

Look at the two pictures below. Which nail will be easier to hammer into the table if the same force is applied in both cases?

Even though the force applied in both cases is the same, the nail with the sharp end is easier to insert. This happens because of pressure.

So pressure can be defined as,

“Pressure is the amount of force pushing straight onto a surface, spread over the area it acts on.”

 
Though the forces applied in both instances in the above activity are the same, the nail with a sharp end is preferred as it will be easier to insert it into the table. This is due to the physical quantity pressure. 

Pressure is defined as the force acting per unit area. Mathematically, it can be expressed as, 

Pressure=ForceArea

 The S.I. unit of pressure is pascal (Pa) or N · m-2.

Numericals on Calculating Pressure

Example 1: If a force of 50 N is applied on an area of 5 m2, calculate the pressure.

Solution: Force = 50 N , Area = 5 m2

Pressure=ForceArea

= 505

= 10 Nm-2 or Pa

 

Example 2: Calculate the pressure if a force of 2000 N is applied on an area of 40 m2.

Solution: Force = 2000 N , Area = 40 m2

Pressure=ForceArea

= 200040

= 50 Nm-2 or Pa

Factors Affecting Pressure

Pressure does not just appear out of nowhere; it depends on how much force is applied and over what area. There are two main factors that affect pressure:

1. Pressure is directly proportional to force. The greater the force, the more the pressure, and the less the force, the less the pressure.

2. Pressure is inversely proportional to area. The greater the area, the less the pressure, and the lesser the area, the more the pressure.

Till now, we have seen that pressure is a fundamental concept in physics that affects everyday life. From nails and knives to walking on snow or lying on soft sand, pressure explains how forces interact with surfaces.