Integrated Science for JHS, Unit 5 to 22

UNIT 20: FORCE AND PRESSURE

Module 20.1: Frictional Force

Meaning of Frictional Force

Frictional force is a force that opposes the motion of an object when it is moving or when there is an attempt to move it on a surface. It acts between two surfaces that are in contact with each other. Friction always acts in the opposite direction to motion or attempted motion.

For example, when a book is pushed across a table, the book eventually slows down and stops. This happens because friction acts between the surface of the book and the table, opposing the movement of the book.

Types of Friction

Static Friction – This type of friction prevents an object from moving when a force is applied to it. For example, when you try to push a heavy table and it does not move immediately, static friction is acting.
Sliding Friction – This occurs when two surfaces slide over each other. For example, pushing a book across a table.
Rolling Friction – This occurs when an object rolls over a surface, such as a wheel rolling on the road. Rolling friction is usually smaller than sliding friction.
Fluid Friction – This occurs when an object moves through a fluid such as air or water. Air resistance is an example of fluid friction.

Factors Affecting Friction

Nature of the surface: Rough surfaces produce more friction than smooth surfaces.
Weight of the object: Heavier objects experience more friction than lighter ones.

Advantages of Friction

Helps us to walk without slipping
Allows vehicles to move and stop using brakes
Enables writing with pen or chalk

Disadvantages of Friction

Causes wear and tear of machine parts
Produces heat, leading to energy loss

Methods of Reducing Friction

Lubrication (using oil or grease)
Polishing surfaces
Using wheels or rollers

Module 20.2: Surface Tension

Meaning of Surface Tension

Surface tension is the force that makes the surface of a liquid behave like a stretched elastic skin. It occurs because the molecules at the surface of a liquid are attracted to each other more strongly than to the air above them.

Explanation of Surface Tension

In liquids, molecules attract each other. Molecules inside the liquid are pulled equally in all directions, but molecules at the surface are pulled inward. This inward pull creates a tight surface known as surface tension.

Examples of Surface Tension

A needle or razor blade floating on water
Water droplets forming round shapes
Insects walking on the surface of water

Importance of Surface Tension

Helps insects like water striders to walk on water
Plays a role in the formation of raindrops
Useful in cleaning when soap reduces surface tension

UNIT 21: INFECTIOUS DISEASES OF HUMANS AND PLANTS

Module 21.1: Meaning of Infectious Diseases

Meaning of Infectious Diseases

Infectious diseases are diseases that are caused by germs or microorganisms and can be transmitted from one person to another, from animals to humans, or through contaminated food, water, or air.

Causes of Infectious Diseases

Infectious diseases are caused by microorganisms such as:

Bacteria
Viruses
Fungi
Parasites

Examples of Infectious Diseases

Cholera
Tuberculosis
Malaria
Measles
COVID-19

Effects of Infectious Diseases

Weakness and illness
Loss of productivity
Death if not properly treated

Module 21.2: Prevention of Infectious Diseases

Ways of Preventing Infectious Diseases

Personal Hygiene – Regular washing of hands with soap and water
Environmental Sanitation – Proper disposal of waste
Vaccination – Immunization against diseases such as measles and polio
Safe Water and Food – Drinking clean water and eating well-cooked food
Use of Insecticide-Treated Nets – Prevents malaria

Importance of Disease Prevention

Reduces the spread of diseases
Promotes healthy living
Reduces healthcare costs

Module 21.3: Good Health Practices

Meaning of Good Health Practices

Good health practices are habits and actions that help to maintain physical, mental, and social well-being.

Examples of Good Health Practices

Eating a balanced diet
Regular exercise
Adequate rest and sleep
Keeping the environment clean
Regular medical check-ups

Benefits of Good Health Practices

Improves body immunity
Prevents diseases
Enhances productivity and longevity

UNIT 22: MAGNETISM

Module 22.1: Magnetic and Non-Magnetic Materials

Meaning of Magnetism

Magnetism is a force produced by a magnet that attracts certain materials.

Magnetic Materials

Magnetic materials are materials that are attracted by magnets. Examples include:

Iron
Steel
Nickel
Cobalt

Non-Magnetic Materials

Non-magnetic materials are materials that are not attracted by magnets. Examples include:

Wood
Plastic
Glass
Rubber

Importance of Magnetic Materials

Used in making electrical appliances
Used in construction and engineering

Module 22.2: Electromagnetism

Meaning of Electromagnetism

Electromagnetism is the production of magnetism using electric current. An electromagnet works only when electric current passes through it.

How an Electromagnet Works

When electric current flows through a coil of wire wrapped around an iron core, the iron becomes magnetized. When the current is switched off, the magnetism disappears.

Advantages of Electromagnets

Can be switched on and off
Strength can be controlled

Uses of Electromagnets

Electric bells
Cranes for lifting scrap metal
Electric motors

Module 22.3: Uses of Magnets

Uses of Magnets in Daily Life

In electric fans and generators
In refrigerators
In loudspeakers
In compasses for navigation

Importance of Magnets

Magnets play an important role in modern technology and everyday life by making work easier and more efficient.