Introduction to Physics
Physics is a field of science that studies how the natural world works. It does this by observing events, gathering information, using simple mathematics to describe what is happening, checking ideas with experiments, and forming clear conclusions.
Meaning of Physics
Physics is the study of nature. It explains how things move, how forces act, how energy behaves, and how matter is structured. The main aim of physics is to understand how the universe works.
Physics is often called the mother of sciences because its ideas support many other fields. The rules of physics apply everywhere, from tiny particles to huge galaxies.
There are two main types of physicists:
- Theoretical physicists: They develop ideas and explain processes using mathematical methods.
- Experimental physicists: They test ideas and conduct experiments to confirm them.
Branches of Physics
Scientists divided physics into many branches to study different areas more clearly. These branches help organize information and make learning easier.
1. Mechanics Mechanics deals with motion, forces, and the laws that control movement.
2. Thermodynamics Thermodynamics studies heat, temperature, energy, and how these affect work.
3. Electricity Electricity explains how electric charges behave when they are at rest or in motion.
4. Magnetism Magnetism studies magnetic materials and how magnetic forces act.
5. Atomic Physics Atomic physics focuses on the structure, behavior, and properties of atoms.
6. Optics Optics studies light, its behavior, and how different instruments help us observe it.
7. Sound Sound explains how sound waves are produced, how they travel, and how they are used.
8. Nuclear Physics Nuclear physics studies the parts of an atomic nucleus, their behavior, and interactions.
9. Particle Physics Particle physics deals with tiny particles that make up matter and radiation, and how they interact.
10. Astrophysics Astrophysics applies the rules of physics to study stars, planets, and other objects in space.
11. Plasma Physics Plasma physics studies matter in the ionized state and how it behaves.
12. Geophysics Geophysics studies the internal structure and physical properties of the Earth.
Importance of Physics in Science Technology and Society
Physics plays a central role in daily life because technology is built on ideas discovered through physics. Many things we use today exist because earlier scientists studied natural processes and explained them clearly.
Important discoveries like magnetism, electricity, and conductors became the basis for modern devices. This led to the creation of televisions, computers, smartphones, medical equipment, and many tools used in homes and workplaces.
Modern transportation systems, including aircraft, and modern communication systems that link people across the world, also depend on the ideas of physics. In simple words, without physics, today’s technology and society would not function the way they do.
MEASURING INSTRUMENTS
Physics deals with matter, energy and how they interact. To understand these interactions, we use different physical quantities. A physical quantity is any measurable property of a body, substance or phenomenon.
Physical Quantity
A physical quantity always has two parts. One part is a number that tells how much. The other part is a unit that tells what we are measuring.
Physical quantities are divided into two main types.
1. Fundamental (Basic) Physical Quantities
These are the basic quantities.
They do not depend on any other quantity for explanation.
All other quantities are built from them.
The seven fundamental quantities with their units are:
Length
S I unit is meter
Symbol is m
Mass
S I unit is kilogram
Symbol is kg
Time
S I unit is second
Symbol is s
Electric current
S I unit is ampere
Symbol is A
Temperature
S I unit is kelvin
Symbol is K
Amount of substance
S I unit is mole
Symbol is mol
Luminous intensity
S I unit is candela
Symbol is cd
2. Derived Physical Quantities
These quantities are formed by combining fundamental quantities.
Their units are also made by combining the S I units of fundamental quantities.
Examples of derived quantities are:
Volume
S I unit is cubic meter
Symbol is m³
Velocity
S I unit is meter per second
Symbol is m s⁻¹
Force
S I unit is newton
Symbol is N
Density
S I unit is kilogram per cubic meter
Symbol is kg m⁻³
Acceleration
S I unit is meter per second square
Symbol is m s⁻²
How physical quantities are measured
Some quantities are measured directly using instruments.
A thermometer measures temperature.
A measuring tape measures length.
A balance measures mass.
Other quantities are calculated using formulas.
For example velocity, density and acceleration are found by using the known values of fundamental quantities.
PREFIXES
What are prefixes
When we measure any physical quantity, we use units.
Sometimes the value of a unit becomes very big or very small.
To make these values easy to read and write, we attach a prefix to the unit.
A prefix shows how many times larger or smaller a unit becomes.
It tells us a multiple or a fraction of the unit.
For example
kilometer means one thousand meters
millimeter means one thousandth part of a meter
Why we use prefixes
They help us avoid writing long numbers.
It is easier to write 5 km instead of 5000 m.
It is easier to write 2 mm instead of 0.002 m.
Prefixes keep measurements simple and clear.
How prefixes work
Prefixes are based on powers of ten.
Each prefix has a fixed value.
For example
kilo means ten to the power three
milli means ten to the power minus three
So by adding a prefix to a unit, we change the size of that unit using a clear and standard method.
Where they come from
Many prefixes were used in history.
Only a small group of prefixes is recognized today by international standards organizations.
These are part of the metric system and are used in science around the world.
SCIENTIFIC NOTATION
What is scientific notation
Scientific notation is a simple way of writing very large or very small numbers.
It helps us avoid long strings of zeros.
In this method, a number is written using a power of ten.
For example
instead of writing 4500000, we write 4.5 × 10⁶
instead of writing 0.00032, we write 3.2 × 10⁻⁴
This makes calculations faster and cleaner.
How a number is written in scientific notation
Every number in scientific notation has three parts:
- Coefficient
This is the main number.
It must be 1 or more, and less than 10.
It cannot be zero. - Base
The base is always 10. - Exponent
The exponent tells how many times we multiply or divide by 10.
It can be positive or negative.
A positive exponent shows a large number.
A negative exponent shows a very small number.
How it works
To change a large number into scientific notation, move the decimal point to make the coefficient between 1 and 10.
Count the number of places you move.
That count becomes the exponent on 10.
To change a very small number, move the decimal point to the right and count the places.
The exponent becomes negative.