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3. Force and Pressure What is Pressure? Pressure = Force ÷ Area Applications of Pressure (skis, sharp blades)
Year 8 • Physics
Force and Pressure
This lesson explains what pressure is, how it is calculated using force and area, and how pressure is applied in everyday life such as skis, sharp blades, snowshoes, and high-heeled shoes.
Lesson Objectives
- Understand what pressure means.
- Use the pressure formula correctly.
- Explain how force and area affect pressure.
- Apply pressure concepts to real-life situations.
1. What Is Pressure?
Pressure is the amount of force applied over a certain area.
It tells us how concentrated a force is.
Important Idea:
The same force can create different pressure depending on the area over which it acts.
The same force can create different pressure depending on the area over which it acts.
2. Pressure Formula
Pressure depends on two things: force and area.
Pressure Formula:
Pressure = Force ÷ Area
Pressure = Force ÷ Area
• Force is measured in newtons (N)
• Area is measured in square metres (m²)
• Pressure is measured in pascals (Pa)
3. Effect of Area on Pressure
Pressure increases when the area decreases and decreases when the area increases.
Key Rules:
• Small area → high pressure
• Large area → low pressure
• Small area → high pressure
• Large area → low pressure
4. Applications of Pressure
Sharp Blades:
Knives and axes have small contact areas, creating high pressure, making cutting easier.
Knives and axes have small contact areas, creating high pressure, making cutting easier.
Skis and Snowshoes:
Large surface area reduces pressure, preventing sinking into snow.
High-Heeled Shoes:
Small area produces high pressure, which is why heels sink into soft ground.
5. Pressure in Everyday Life
• Camels have wide feet to reduce pressure on sand
• Tractors use wide tyres to avoid sinking into soil
• Nails have sharp tips to apply high pressure
• Tractors use wide tyres to avoid sinking into soil
• Nails have sharp tips to apply high pressure
Practice Questions
A. Fill in the Blanks
- Pressure is force divided by __________.
- Pressure is measured in __________.
- A smaller area creates __________ pressure.
- Force is measured in __________.
- Skis reduce pressure by increasing __________.
B. True or False
- Pressure depends only on force.
- Sharp knives cut better due to high pressure.
- Large area produces high pressure.
- Pressure is measured in newtons.
- Wide tyres reduce pressure.
C. Short Answer
- Define pressure.
- Write the pressure formula.
- Why do camels have wide feet?
- Why do sharp objects exert more pressure?
- Name two applications of pressure.
D. Numerical Problems
- A force of 100 N acts on an area of 2 m². Calculate pressure.
- A force of 50 N acts on an area of 0.5 m². Find pressure.
- A force of 200 N acts on an area of 4 m². Calculate pressure.
- What force acts if pressure is 10 Pa on area 2 m²?
- Find area if force is 40 N and pressure is 20 Pa.
✅ Show Answer Key
A. Fill in the Blanks
- area
- pascals
- higher
- newtons
- area
B. True or False
- False
- True
- False
- False
- True
C. Short Answer
- Pressure is force acting per unit area.
- Pressure = Force ÷ Area.
- To reduce pressure on sand.
- They act over a smaller area.
- Knives, skis (any two).
D. Numerical Problems
- 100 ÷ 2 = 50 Pa
- 50 ÷ 0.5 = 100 Pa
- 200 ÷ 4 = 50 Pa
- Force = 10 × 2 = 20 N
- Area = 40 ÷ 20 = 2 m²
© Aviate Learning – Force and Pressure (Year 8)