Pressure concept - Simulator

PRESSURE

Understand Force, Area and Pressure Through Experiments

Interactive Physical Science Laboratory

Explore • Observe • Calculate • Learn

Learning Objectives

• Understand the meaning of pressure.
• Understand the relationship between force, area and pressure.
• Calculate pressure using the mathematical formula.
• Compare pressure for different positions of objects.
• Understand pressure in solids, liquids and gases.
• Explore daily-life applications of pressure.

📚 Interactive Index

Select a topic to jump directly to that section. Use the audio button to listen to the explanation.

01. Meaning of Pressure

👞 ⬇️ 🟫

Pressure is the force acting perpendicularly on a unit area of a surface.

Pressure = Force ÷ Area

When a force acts on a smaller area, the pressure is greater. When the same force acts on a larger area, the pressure is smaller.

Example: A pointed nail enters wood easily because its pointed end has a very small area of contact. The same force produces greater pressure.

02. Mathematical Formula of Pressure

P = F / A

Where:

• P = Pressure
• F = Perpendicular force in newtons
• A = Area of contact in square metres

Important: The force used in the formula is the perpendicular component of force acting on the surface.

Try a simple calculation

Force (N)

Area (m²)

Pressure = Force / Area

50 Pa

100 / 2 = 50 Pa

03. Units of Pressure

The SI unit of pressure is the pascal, represented by Pa.

1 Pa = 1 N/m²

• 1 pascal = 1 newton per square metre.
• 1 kilopascal = 1000 pascals.
• 1 megapascal = 1,000,000 pascals.

Other units used in science include atmosphere, bar and millimetres of mercury.

04. Interactive Experiment: Pressure Exerted by a Brick

Aim: To investigate how the area of contact affects pressure when the force remains constant.

Apparatus: Rectangular brick, horizontal surface, measuring scale and weighing balance.

Procedure:

1. Measure the mass of the brick.
2. Calculate its weight using W = m × g.
3. Place the brick on its largest face.
4. Measure the area of contact.
5. Calculate the pressure.
6. Rotate the brick onto its smallest face and repeat.

Safety: Handle heavy objects carefully. Keep fingers away from underneath the brick. Perform the experiment on a stable surface.

Perform the Brick Simulation

Select the brick position Horizontal - Largest face on ground Vertical - Smallest face on ground Side position - Medium face on ground Brick mass (kg)

Mass: 5 kg

Length (cm) Width (cm) Height (cm)

↓ F = Weight

BRICK

Force of gravity
49 N

Area of contact
0.02 m²

Calculated pressure

2450 Pa

Pressure on largest face

The brick is resting on its largest face.

Assumption: g = 9.8 m/s². The brick is uniform and rests flat on the surface. The displayed contact area is the full face touching the ground.

Observation Table

Position	Contact area	Force	Pressure

05. Compare Different Objects and Contact Areas

Select an object and change its orientation. The simulation calculates its weight, area of contact and pressure.

Select an object Rectangular brick Textbook Rectangular eraser Wooden block Rectangular box Metal cuboid Position Horizontal - Largest face Vertical - Smallest face Side position - Medium face Mass (kg)

Mass: 5 kg

↓ Weight

OBJECT

Weight: 49 N

Contact area: 0.02 m²

Pressure

2450 Pa

The sample dimensions and masses are illustrative. You can change the mass and orientation to explore the relationship. For an actual object, measure its dimensions and mass.

06. What Happens When Force and Area Change?

Explore the effects of changing force and area independently.

Experiment A: Constant Force

Keep force constant at 100 N. Change the area.

Area (m²)

Area: 1 m²

Pressure:

100 Pa

Experiment B: Constant Area

Keep area constant at 1 m². Change force.

Force (N)

Force: 100 N

Pressure:

100 Pa

07. Applications of Pressure in Daily Life

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Sharp knives

A sharp edge has a smaller contact area, producing greater pressure and making cutting easier.

📌

Pointed nails

The pointed end of a nail produces high pressure and enters wood easily.

🐘

Elephant's feet

Broad feet spread the weight over a larger area and reduce pressure on the ground.

🎿

Snow shoes and skis

Wide skis increase contact area and reduce pressure, preventing a person from sinking deeply into snow.

🏗️

Building foundations

Wide foundations distribute the building's weight over a larger area of soil.

🎒

Broad school-bag straps

Broad straps distribute the force over a larger area of the shoulder and reduce pressure.

🧱

Wide tyres

Wider tyres can distribute the load over a larger contact area, subject to tyre pressure and construction.

👠

High heels

A narrow heel has a smaller contact area and exerts greater pressure on the ground.

08. Pressure in Liquids

Liquids exert pressure on the bottom and walls of their containers. Liquid pressure increases with depth.

P = ρgh

• ρ = Density of liquid in kg/m³
• g = Acceleration due to gravity in m/s²
• h = Depth below the liquid surface in metres

This formula gives gauge pressure due to the liquid column. Absolute pressure also includes atmospheric pressure.

Explore Water Pressure at Different Depths

Depth below water surface (m)

Depth: 5 m

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WATER

Water pressure (gauge)

49,000 Pa

Assume water density = 1000 kg/m³ and g = 9.8 m/s². The simulation shows hydrostatic gauge pressure.

Important Properties of Liquid Pressure

• Liquid pressure increases with depth.
• At the same depth in the same liquid, pressure is equal.
• Liquid pressure acts in all directions.
• Liquid pressure depends on the density of the liquid.
• For a stationary liquid, pressure at a given depth does not depend on the shape of the container.

09. Atmospheric Pressure

🌍 ☁️

Air surrounds the Earth. The weight of the air column produces atmospheric pressure.

Standard atmospheric pressure = 101325 Pa

At sea level, standard atmospheric pressure is approximately 1.013 × 10⁵ Pa.

Examples demonstrating atmospheric pressure

• Drinking through a straw.
• Working of a syringe.
• Working of a suction cup.
• Changes in air pressure with altitude.
• Crushing of a can due to atmospheric pressure when the pressure inside is reduced.

10. Pressure in Solids, Liquids and Gases

Solids: A solid exerts pressure on the surface on which it rests due to its weight or applied force. Pressure depends on the contact area.

Liquids: Liquids exert pressure on the bottom and walls of a container. Pressure increases with depth.

Gases: Gas molecules move continuously and collide with the walls of their container, producing pressure.

11. Solved Numerical Problems

Problem 1

A force of 200 N acts on an area of 4 square metres. Find the pressure.

Solution:

P = F / A = 200 / 4 = 50 Pa

Answer: 50 Pa

Problem 2

A brick weighing 100 N rests on an area of 0.05 m². Calculate the pressure.

Solution: P = 100 / 0.05 = 2000 Pa.

Answer: 2000 Pa

Problem 3

A pressure of 500 Pa acts over an area of 2 m². Calculate the force.

Solution: F = P × A = 500 × 2 = 1000 N.

Answer: 1000 N

Problem 4

Water is at a depth of 3 m. Calculate the gauge pressure at that depth.

Solution: P = ρgh = 1000 × 9.8 × 3 = 29400 Pa.

Answer: 29400 Pa

12. Student Assessment

Answer the following questions and check your understanding.

1. What is the SI unit of pressure? Newton Pascal Joule Watt

2. Pressure is equal to: Force × Area Area / Force Force / Area Mass × Area

3. If the same force acts on a smaller area, pressure: Increases Decreases Becomes zero Remains unchanged

4. A brick is placed on its smallest face. The pressure is generally: Minimum Maximum Zero Unchanged from every position

5. The standard atmospheric pressure at sea level is approximately: 100 Pa 1000 Pa 101325 Pa 10 Pa

6. Liquid pressure increases with: Colour Depth Container colour Surface area alone

7. A force of 60 N acts on an area of 3 m². Pressure is: 180 Pa 20 Pa 63 Pa 10 Pa

8. Broad school-bag straps are useful because they: Increase pressure Increase weight Reduce contact area Reduce pressure

9. The pressure exerted by a liquid depends on: Density and depth Colour only Container shape only Temperature only

10. A force of 100 N produces a pressure of 50 Pa. The area is: 0.5 m² 2 m² 50 m² 500 m²

Remember These Key Points

• Pressure is force per unit area.
• P = F / A.
• SI unit: pascal (Pa).
• For constant force, pressure decreases as area increases.
• For constant area, pressure increases as force increases.
• Liquid pressure increases with depth.
• Atmospheric pressure is caused by the weight of air.

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