Chapter 3 · ICSE Class 8 Physics (Selina Concise)

Force and Pressure

Explore different types of force, and understand pressure as force distributed over an area.

💪 Chapter 3

The same force applied over a smaller area creates more pressure A force of 100 newtons applied over a large area of 10 square metres gives low pressure, while the same force applied over a small area of 2 square metres gives much higher pressure Area = 10 m² Pressure = 10 Pa Area = 2 m² Pressure = 50 Pa Same force (100 N), smaller area = more pressure
3.1

Types of Force

Forces include muscular, friction, magnetic, electrostatic, and gravitational force, each acting differently on objects.

1

What type of force allows you to walk without slipping?

Friction force, between your shoes and the ground

2

What type of force causes a balloon rubbed on hair to attract small paper pieces?

Electrostatic force

3.2

Understanding Pressure

Pressure = force/area. The same force spread over a smaller area creates greater pressure.

1

Why does a sharp knife cut more easily than a blunt one, with the same force applied?

The sharp edge has a much smaller area, so the same force creates much greater pressure, making it easier to cut

2

A force of 100N acts on an area of 2m². Find the pressure.

100/2=50 N/m² (Pascals)

Practice

Exercises

1. Name three types of force.

2. What is the formula for pressure?

3. A force of 60N acts on an area of 3m². Find the pressure.

4. Why do wide tyres reduce pressure on soft ground?

5. What is the SI unit of pressure?

Next chapter — Energy ⚡ →