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Yes, there are many such quantities which have no dimension as well as no unit. 

For example:

1. A strain is dimensionless and unitless.

2. Angle and solid angle also belong to this category.

The velocity of a body
11 = A + Bt

On applying the principle of homogeneity, The dimensional formula of A = Dimensions of v.

= \([M^0L^1T^{-1}]\)

Similarly, the dimensions of Bt = Dimensions of v
∴ Dimensions of B = dimensions of v/l

Given relation,

F = a + bx

Applying the principle of homogeneity of dimensions. We have,

Dimensions of a = dimensions of F
= \([M^1L^1T^{-2}]\)

Dimension of bx = dimensions of F

Dimensions of b = dimensions of F/x

Radian : The plane angle is given by

\(d \theta = \frac{ds}{r} rad\)

If ds = r, then \(d \theta\) = 1rad

Thus, “One radian is the angle subtended at the centre of a circle by an arc equal in length to the radius of the circle.”

Conversion of units of physical quantities from one system to another system: The method of dimensional analysis can be used to obtain the value of the physical quantity in some other system when its value in one system is given.
As discussed earlier, the measurement of a physical quantity is given by:
Q = nu
If the unit of a physical quantity in a system is u₁, and the numerical value is n₁, then:
Q = n₁u₁ …………….(1)
Similar in the other system if the unit is u₂ and magnitude is n₂ then:
Q= n₂u₂ …………………..(2)
From Eqs. (1) and (2)
n₁u₁ = n₂u₂ ……………..(3)

If a,b,c are the dimensions of a physical quantity in mass, length and time, then: 

Here M₁ ,L₁ ,T₁ and M₂ ,L₂ ,T₂ are the units of mass, length and time in the two systems, then

The equation can be used to find out the value of a physical quantity in the second or the new system, when its value in first system is known.

Angle, Refractive index

Quantities of S.I. system of units :
The French name of this system is “Le System International d Units”. It is abbreviated as S.I. system. It has seven fundamental (or basic) units and two supplementary units.

Fundamental quantities: Length, mass, time, electric current, temperature, luminous intensity and amount of substance.
Supplementary quantities : Plane angle, and solid angle.

Unit : “Unit is a standard quantity of the same kind with which a physical quantity is compared for its measurement.” 

In the process to know or express the magnitude of a physical quantity ‘Q terms of :

(i) Size of unit (u) used.

(ii) The numerical value of the unit. So, Q = nu

If the size of the unit is changed then the value of n will also change for the same amount of physical quantity Question, Therefore.
\(Q = n_1u_1 = n_2u_2 = n_3u_3 = \dots\)
⇒ nu = Constant

1. C.G.S. System: It is a French system of units. In this system, length is measured in centimeters (cm), mass is measured in grams (g) and time is measured in seconds (s).

2. M.K.S. System: It is also a French system of units. In this system, length is measured in meters (m), mass in kilograms (kg) and time in seconds (s).

F.P.S. System: It is a British system of units. In this system the length is measured is foot (l), mass in pounds (p) and time in seconds (s).

Unit of energy is 4 times.

\(m \frac{\triangle x}{x} \times 100 \%\)

(i) The gravitational forces,

(ii) The electromagnetic force,

(iii) The strong nuclear force and

(iv) The weak nuclear forces are the four fundamental forces in nature.

Physical quantity that remains unchanged in a process is called conserved quantity.

The forces are: 

• Gravitational force 
• Electromagnetic force 
• Strong nuclear force strongest 
• Weak nuclear force

(a) The nuclear force is the strongest.

(b) Gravitational force is weakest.

Gravitational force.

Dr. Homi Jehangir Bhabha.

C.V.Raman and S.Chandra Shekhar.

(a) The study of satellite has made it possible to forecast the weather very accurately.

(b) Due to the discovery of nuclear fission, a large amount of energy becomes available in nuclear power station due to conversion of mass into energy.

1. Mechanics, 

2. Heat & Thermodynamics, 

3. Electromagnetism 

4. Theory of relativity, 

5.Quantum mechanics.

(a) Thomson, (b) Newton.

Christian Huygens.

The interplay of theory and observation (or experiment) is basic to the progress of science.

The basic aim of science is to search for the truth and anlyse the natural phenomena that are taking place in the surroundings.

The word is ‘fusis' meaning ‘nature’.

The following factors have in fact hindered the advancement of science in India:

(a) Migration of scientists, doctors technologists and engineers to other countries because those countries provide excellent laboratory infrastructure as well as salary,which our country does not provide yes.

(b) Scientists and technologists are not given the required academic freedom to pursue their goals.

(c) Lack of coordination between the researchers and the industrialists. Indian industrialists even today like to import technology and give support to do advance research. The industrialists do not develop research infrastructure in our country as in some of advanced countries.

(d) Excess of administrative interference in management of research and technology.

The attempts to unify fundamental forces of nature is the quest for unification phenomena in terms of a few concepts and laws. A related effort to drive the properties of a bigger, more complex, system from the properties and interactions of its constituent simpler parts, is called reduction approach in physics.

Science is a systematic attempt to understand a natural phenomenon in as much detail and depth as possible and use the knowledge so gained to predict, modify and control phenomenon.

Some key contemporary areas of technology and Science, which are chiefly responsible for a new industrial revolution taking place now and likely to take place in the near future are:

• Artificial intelligence
• Design of super-fast computers.
• Biotechnology
• Development of superconducting materials at room temperature.
• Advancements in the field of

→ Electronics

→ Information technology

→ Nanotechnology

→ Developments in the field of Space Sciences

Bhautika the name of Sanskrit equivalent word of physics.

In Sanskrit (Hindi) it is Vignam and in Arabic(Urdu) it is llm for science.

It is comprehensible.

The following examples can be exciting, at the same time educative too:

(a) The heat energy of steam runs an engine.

(b) The study of electricity and magnetism helps us to design dynamos and motors.

(c) The beating of the drum causes vibrations, producing huge sound,can pollute air and even make people mad and deaf.

(d) The fall of an apple leads us to understand gravity

(e) A spherical liquid drop, and it never takes any other geometrical shape, helps us to understand surface tension.

The followings are the two examples of gravitational forces:

(a) The force of attraction between various bodies in the universe is the gravitational force. It is the gravitational force which has assembled an present plants stars and galaxies.

(b) The weight of the body is the force with which the earth attracts the body to wards its centre is the example of gravitational force.

Organized knowledge.

θ = Δmc², where θ is energy released or absorbed Δm is the mass of matter and c is the speed of light.

The study of physics is exciting in many ways e.g., 

(i) Journey to the moon is controlled from the ground.

(ii) Lasers and their ever-increasing applications.

(iii) Live transmission of events thousands of kilometers away on the T.V.

(iv) The speed and memory of the fifth generation of computers.

(v) Study of various types of forces in nature.

(vi) Technological advances in health science.

(vii) Use of robots is quite exciting.

(viii) Telephone calls over long distance and so on. Thus, physics is exciting not only to the scientists but also to a lay man, children, women etc. All the musical instruments, toy guns, toy trains etc. all are constructed using simple principles of physics like collision, potential energy etc. Today the situation is that even our thought process and social values are affected by physics. Thus, it is quite amazing.

Physics is an efforts at seeking the ultimate truth about the physical would. The physicists believes that mankind will continue to get closer and closer to the ultimate truth. A major preoccupation of physicists is the study of elementary particles, their properties and their interactions. only four fundamental interactions listed below, have been discovered so far. All the observed forces and interactions in the universe can be broadly based on these interactions:

(a) Gravitational interaction,

(b) Weak interaction,

(c) Electromagnetic interaction,

(d) Nuclear interaction.

The interactions vividly bring about the concepts of both 'a very tiny world' and 'a very large world'. The laws of physics which rule stars and galaxies also govern elementary particles.

physics plays a crucial role in technology. The outstanding contributions of physics to technology are radio-engineering and electronics. Prior to this, the outstanding contributions were electricity, aviation, aerodynamics and hydrodynamics. If we go back to three hundred years back, we shall find the pioneer Italian physicist Galileo, trying to find out the ways and means to support heavy beams without breaking them.

Physics is the key to the answer of questions-involving the behaviour of non- living things in nature. What are electrons? What are atoms? What are molecules? How do the sum and stars produce intense heat and light ? Is it possible to create of destroy matter? What holds protons and neutrons together in the nucleus? A number of such questions can be answered by physics.

This society of ours has become more and  more Science-oriented. Even those of us who do not plan to become direct does of science will be better members of society if we develop an understanding of the basic laws of physics.

Astronomy is the branch of science that deals with the study of stars.

What do we see around us? It is nature spread all around in all its manifestations. We could see a lot many natural phenomena around us every moment-like the rainfall, lightning thunder, cloud formations change of season, change of day into night and vice-versa, birth of a child, death of an old man, crops- growing, etc. we find a distant person could talk to other in a flash of a second without crossing seas and miles, we see a distant person talking, acting, singing, dancing in T.V. and so on. We become cursious to know about all there happening in fact, everybody wishes to unfold the mysteries of nature. It is physics, which unfolds the curtains from there misteries. That is why physics is also known as natural science. Which also includes other disciplines like chemistry and biology. we can broadly describe physics as a study of the basic laws of nature and their manifestation different natural phenomena.

So,we can conclude that physics is the science of nature.

Those science which deal with living things are called biological science, e.g., Zoology, Botany, Ornithology.

Physics is considered to be the mother of all sciences.

Politicians make anything and everything possible to win votes. Science is a systematized study of observation. Scientist and researchers study these observations and then work out certain laws from them. There is a multitude of natural phenomena taking place in this universe and all of them can be explained in terms of some basic laws. 

For e.g. F = mg is true for you and me and also for a star. Thus, in science we see that various phenomena are related, they are soluble and can be explained with similar or the same law. This goes on to justify that science is the art of the soluble just as politics is the art of the possible.

Science is the study of natural phenomena in much depth and details as possible and application of such knowledge obtained to predict modify and control the phenomena.

The physical world means the collections of all living and non- living things in our surroundings.

Einstein worked to establish a relation between the energy and mass of body. He was of the view that these are the two sides of the same coin or two facts of the simple physical quantity. He succeeded when the gave his mas energy equation E = mc² . But its experimental verification came 40 year later in 1945 when atomic bomb was exploded over japan.

Science has helped in solving food problems in the following ways:

(i) It has introduced new agriculture implement.

(ii) Science has improved the quality of seeds by genetic engineering.

(iii) High yielding hybrid variety of grains have been developed. Some easily reaping varieties have also been developed and grown.

(iv) Use of pesticides and insecticides have saved crop from being destroyed by the insects and pests.

(v) Some new type of crops are also developed and are being developed to meet the requirement of the society.

The given relation,

1/2mv = mgh  ......(1)

The dimensional formula of L.H.S.

= [M¹L¹T^-1] 

and the dimensional formula of R.H.S.

\(\begin{array}{l}{=\left[\mathrm{M}^{1} \cdot \mathrm{L}^{1} \mathrm{T}^{-2}\right]{L}^{1} \mathrm{J}} \\ {=\left[\mathrm{M}^{1} \mathrm{L}^{2} \mathrm{T}^{-2}\right]}\end{array}\)

Since the dimension of both the sides are not equal, therefore given relation is “incorrect”.

(i) Charles Babbage, (ii) J. Bardeen, (iii) A. Edison, (iv) Apleton, (v) Marconi, (vi) Graham Bell.

The inclination to solving problems by adopting scientific method is know as scientific attitude.

Hess, Austria.