CBSE Class 11 Physics Physical World And Measurement Notes

Download CBSE Class 11 Physics Physical World And Measurement Notes in PDF format. All Revision notes for Class 11 Physics have been designed as per the latest syllabus and updated chapters given in your textbook for Physics in Class 11. Our teachers have designed these concept notes for the benefit of Class 11 students. You should use these chapter wise notes for revision on daily basis. These study notes can also be used for learning each chapter and its important and difficult topics or revision just before your exams to help you get better scores in upcoming examinations, You can also use Printable notes for Class 11 Physics for faster revision of difficult topics and get higher rank. After reading these notes also refer to MCQ questions for Class 11 Physics given on studiestoday

Revision Notes for Class 11 Physics Chapter 1 Physical World

Class 11 Physics students should refer to the following concepts and notes for Chapter 1 Physical World in Class 11. These exam notes for Class 11 Physics will be very useful for upcoming class tests and examinations and help you to score good marks

Chapter 1 Physical World Notes Class 11 Physics

PHYSICAL WORLD 

MAIN POINTS

√  Physics deals with the study of the basic laws of nature and their manifestation in different phenomena. The basic laws of physics are universal and apply in widely different contexts and conditions.

√  The scope of physics is wide, covering a tremendous range of magnitude of physical quantities.

√  Physics and technology are related to each other. Sometimes technology gives raise to new physics at other times physics generates new technology. Both have direct impact on society.

√  There are four fundamental forces in nature that govern the diverse phenomena of the macroscopic and the microscopic world. These are the ‘gravitational force ‘, the electromagnetic force’, ‘the strong nuclear force’, and the weak nuclear force’

√  The physical quantities that remain unchanged in a process are called conserved quantities. Some of the general conservation laws in nature include the law of conservation of mass, energy, linear momentum, angular momentum, charge, parity, etc. 

√  Conservation laws have a deep connection with symmetries of nature .symmetries of space and time, and other types of symmetries play a central role in modern theories of fundamental forces in nature.

√  Gravitational force is the force of mutual attraction between any two objects by virtue of their masses. It is always attractive

√  Electromagnetic Force is the force between charged particles .It acts over large distances and does not need any intervening medium. Enormously strong compared to gravity.It can be attractive or repulsive. 

√  Strong nuclear force is the force that binds the nucleons together.It is the strongest of all the fundamental forces. It is charge independent. And very short range.

√  Weak nuclear force appears only in certain nuclear processes such as β-decay. Weak nuclear force is not as weak as the gravitational force.

√  In a chemical reaction if the total binding energy of the reacting molecules is less than that of the product molecules the difference appears as heat and the reaction is exothermic

√  In a chemical reaction if the total binding energy of the reacting molecules is more than that of the product molecules the difference amount of energy is absorbed and the reaction is endothermic.

√  In a nuclear process mass gets converted into energy. This is the energy which gets released in a nuclear power generation and nuclear explosions.

There are four fundamental forces which govern both macroscopic and microscopic phenomena. There are

(i) Gravitational force             (iii) Electromagnetic force

(ii) Nuclear force                   (iv) Weak force

The relative strengths of these forces are

                        Fg :Fw:Fe:Fs=1:1025:1036:1038 .

All those quantities which can be measured directly or indirectly and in terms of which the laws of physics can be expressed are called physical quantities.

(a) Fundamental quantities            (b) Derived quantities.

The units of the fundamental quantities called fundamental units , and the units of derived quantities called derived units.

System of units:-

(a) MKS                (b) CGS                  (c) FPS           (d) SI

• The dimensions of a physical quantity are the powers to which the fundamental quantities are raised to represent that physical quantity.

• The equation which expresses a physical quantity in terms of the fundamental units of mass, length and time, is called dimensional equation.

• According to this principle of homogeneity a physical equation will be dimensionally correct if the dimensions of all the terms in the all the terms occurring on both sides of the equation are the same.

• If any equation is dimensionally correct it is not necessary that must be mathematically correct too.

 

 There are three main uses of the dimensional analysis-

(a) To convert a unit of given physical quantities from one system of units to another system for which we use

n2 = n1[M1/M2]a[L1/L2]b[T1/T2]c

(b) To check the correctness of a given physical relation.

(c) To derive a relationship between different physical quantities.

• Significant figures: - The significant figures are normally those digits in a measured quantity which are known reliably plus one additional digit that is uncertain.

For counting of the significant figure rule are as:

(i) All non- zero digits are significant figure.

(ii) All zero between two non-zero digits are significant figure.

(iii) All zeros to the right of a non-zero digit but to the left of an understood decimal point are not significant. But such zeros are significant if they come from a measurement.

(iv) All zeros to the right of a non-zero digit but to the left of a decimal point are significant.

(v) All zeros to the right of a decimal point are significant.

(vi) All zeros to the right of a decimal point but to the left of a non-zero digit are not significant. Single zero conventionally placed to the left of the decimal point is not significant.

(vii) The number of significant figures does not depend on the system of units.

• In addition or subtraction, the result should be reported to the same number of decimal places as that of the number with minimum number of decimal places.

 In multiplication or division, the result should be reported to the same number of significant figures as that of the number with minimum of significant figures.
 Accuracy refers to the closeness of a measurement to the true value of the physical quantity and precision refers to the resolution or the limit to which the quantity is measured.
 Difference between measured value and true value of a quantity represents error of measurement.
It gives an indication of the limits within which the true value may lie.
Mean of n measurements
amean = a1 + a2 + a3 +....+ an / n

Absolute error ( Δa ) = amean - ai Where ai = measured value It may be - positive, negative or zero.
(i) Mean absolute error
(ii) Relative error - it is the ratio of the mean absolute error to the true value.
δa = I Δa I/ amean
(iii) The relative error expressed in percent is called percentage error.

The error is communicated in different mathematical operations as detailed below:
(i) For x = (a ± b),                       Δx = ± ( Δa + Δb)
(ii) For x = a x b ,                        Δx/x = ± ( Δa/a + Δb/b)
(iii) For x = a/b ,                          Δx/x = ± ( Δa/a + Δb/b)
(iv) For x= anbm /cp                     Δx/x = ± ( nΔa/a +m Δb/b + pΔc/c


Very short answer type questions, (1 mark question)
Q1. State one law that holds good in all natural processes.
Ans. One such laws is the Newton’s gravitation law, According to this law everybody in this nature are attracts with other body with a force of attraction which is directly proportional to the product of their masses and inversely proportionally To the square of the distance between them.

Q2: Among which type of elementary particles does the electromagnetic force act?
Ans : Electromagnetic force acts between on all electrically charged particles.

Q3. Name the forces having the longest and shortest range of operation.
Ans : longest range force is gravitational force and nuclear force is shortest range force.

Q4. If ‘slap’ times speed equals power, what will be the dimensional equation for ‘slap’?
Ans . Slap x speed = power
Or slap = power/speed = [MLT-2]

Q5. If the units of force and length each are doubled, then how many times the unit of energy would be affected?
Ans : Energy = Work done = Force x length
So when the units are doubled, then the unit of energy will increase four times.

Q6. Can a quantity has dimensions but still has no units?
Ans : No, a quantity having dimension must have some units of its measurement.
Q7. Justify L +L = L and L – L =L.

Chapter 04 Motion in a Plane
CBSE Class 11 Physics Motion In Plane Notes
Chapter 06 Work Energy and Power
CBSE Class 11 Physics Work Energy And Power Notes
Chapter 09 Mechanical Properties of Solids
CBSE Class 11 Physics Mechanical Properties Of Solids Notes

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CBSE Class 11 Physics Chapter 1 Physical World Notes

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Chapter 1 Physical World CBSE Class 11 Physics Notes

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