Physics and it’s Quantities

  INTRODUCTION TO PHYSICS

Physics is a branch of science that deals with the matter and energy.

Matter is a substance that has mass and occupies space. It exists in 3 physical states:

• Solid– They have definite volume and shape.
• Liquid– They have definite volume but they lack in having definite shape, they take the shape of the container.
• Gas– They does not possess definite volume and shape. They take the shape of the container in which they are placed.

The fourth physical state of matter is plasma. It is concluded that in the universe, 98% of the matter is in plasma form and rest 2% is in the form of solid, liquid or gas.

Plasma  is found on the surface of the sun and the stars, at the center of the earth too it is abundant.

Thus, physics can be defined as the branch of science that deals with the measurement of the physical quantities.

Physical quantities are the measurable quantities. They have a definite magnitude. They may or may not have a direction.

Types of Physical Quantities

They are of 2 types:

1. Scalar: The physical quantity that has only magnitude is known as scalar quantity.

Ex- Work, Energy, Power etc.

2. Vector: the physical quantity that has both magnitude and direction is known as vector quantity.

Ex- Displacement, Velocity, Acceleration etc.

• Physical quantity is represented by N U (N-Numerical U-Unit).
• The measurements for the physical quantity were first introduced by Lord Kelvin.
• the standard fixed value for the physical quantities are known as

System/Units	Length	Mass	Time
F.P.S	Foot	pound	sec
C.G.S.	Cm	gm	sec
M.K.S.	M	kg	sec

FPS units are called as the British system.

CGS units are called as the French system.

CGS/MKS system is called Metric or Decimal system.

In 1960, the SI units were derived from the M K S units. SI means Standard International followed throughout the world

Quantity	Largest unit	Smallest unit
Length	Parsec1 Parsec= 3.26 Light Years	Fermi 10-15 m1 Fermi=
Mass	Chandra Shekhar Limit (CSL)1 CSL= 1.4 X 2 X 1030 kg	Atomic mass unit (amu)1 amu= 1.66 X 10-27 kg
Time	Cosmic Year (CY)1 CY= 250 Million Years	Shake1 Shake=  10-8 sec

Note: Shake is used in the Atomic expressions.

Light year is the distance traveled by the light in vacuum in one year time. It is a unit of distance not time.

1 LY= 9.46 * 10¹⁵ m

Q.1. Which amongst the following is the state of matter?

1. Plasma
2. Gas
3. Liquid
4. All

Ans. d

Q.2. FPS is abbreviated for:

1. m kg sec
2. foot pound sec
3. cm gm sec
4. feet pound sec

Ans. b

Q.3. CGS is abbreviated for:

1. cm gallon sec
2. foot pound sec
3. cm gm sec
4. feet pound sec

Ans. c

Q.4. 1 light year is equal to:

9. 9.46 * 10¹⁵ m
10. 9.45 * 10¹⁵ m
11. 9.46 * 10¹⁴ m
12. 9 * 10¹⁵ m

Ans. a

Q.5 Choose the vector quantity:

1. Work

b.Energy

1. Power
2. Displacement

Ans. d

Q.6. Choose the scalar quantity:

1. Displacement
2. Acceleration
3. Velocity
4. Work

Ans d

Q.7. Scalar quantities have:

1. Magnitude
2. Direction
3. None
4. Both

Ans. a

Q.8. Vector quantities have:

1. Magnitude
2. Direction
3. None
4. Both

Ans. d