## CBSE - MCQ Question Banks (के. मा. शि. बो . -प्रश्नमाला )

Q. 101 If ‘G’ represents gravitational force, ‘W’ represents weak interactions, ‘E’ represents electromagnetic forces and ‘N’ represents nuclear forces. Then the correct order of their strength would be

A. W

B. G

C. G

D. E

#### SOLUTION

If G is considered  to be 1 unit       then W= 1025 units              E = 1036 units                     N = 1039 units       hence the order is G

Q. 102 Enormous amount of energy released in a nuclear reaction is related to mass by which of the following relation?

A. E = mc

B. E3 = m2c2

C. E = mc2

D. E = mc2

#### SOLUTION

Einstein’s mass-energy equivalence relation is E = mc2 According to Einstein a mass m is equivalent to energy mc2 has led to the unification of the two laws i.e. law of conservation of mass and energy.

Q. 103 Law of isotropy of space states that

A. The space possesses the same properties at all the points

B. If and are linear momenta of the two bodies at any instant, then in the absence of external force, C. The space possesses the same properties in all the directions.

D. Energy can neither be created nor destroyed

#### SOLUTION

Isotropy means uniformity in all orientations.

Q. 104 Nuclear forces are

A. short range force

B. long range forces

C. weaker than gravitational force

D. central forces

#### SOLUTION

The nuclear force between the nucleons exists only when they are inside the nucleus and hence it is a short range force.

Q. 105 Which of the following statements is incorrect?

A. Rocket propulsion is based on Newton's laws of motion.

B. J.J. Thomson discovered electron.

C. Maxwell unified terrestrial and celestial mechanics.

D. Archimedes gave the principle of buoyancy.

#### SOLUTION

Isaac Newton unified terrestrial and celestial mechanics in 1687.

Q. 106 Name the scientist whose field of work was elasticity.

A. Robert Hook

#### SOLUTION

Robert Hook

Q. 107 Who discovered the phenomenon of neutron induced fission of uranium

#### SOLUTION

In 1998 Hahn and Meitner discovered the phenomenon of neutron induced fission of uranium

Q. 108 Name the device which is based on amplification of light by population inversion

#### SOLUTION

Laser

Q. 109 The basic laws of electromagnetism (Maxwell’s equations) govern all electric and magnetic phenomena. This reflects the concept of

A. unification.

B. reductionism.

C. unification and reductionism.

D. deduction.

#### SOLUTION

In Physics, attempts have been made to explain diverse physical phenomena in terms of a few concepts and laws. The effort is to see the physical world as manifestation of some universal laws in different domains and conditions. The attempts to unify fundamental forces of nature reflect the same quest for unification.

Q. 110 According to Einstein’s theory, mass m is equivalent to energy E given by the relation:

A. E=1/2 mv2.

B. E=mgh.

C. E=mc2.

D. E=mc.

#### SOLUTION

According to Einstein’s theory, mass m is equivalent to energy E given by the relation E= mc2, where c is speed of light in vacuum.

Q. 111 For motion under an external

A. non-conservative force, the total mechanical energy i.e. the sum of kinetic and potential energy of a body, remains constant.

B. conservative force, the total mechanical energy i.e. the sum of kinetic and potential energy of a body remains constant.

C. conservative force, the total mechanical energy i.e. the sum of kinetic and potential energy of a body does not remain constant.

D. mechanical force, the total mechanical energy i.e. the sum of kinetic and potential energy of a body remains constant.

#### SOLUTION

This statement can be best explained with this example - the free fall of an object under gravity. Both the kinetic energy of the object and its potential energy change continuously with time, but the sum remains fixed. If the object is released from rest, the initial potential energy is completely converted into the kinetic energy of the object just before it hits the ground.

Q. 112 The force that governs the structure of atoms and molecules, the dynamics of chemical reactions and the mechanical, thermal and other properties of materials is

A. gravitational force.

B. electromagnetic force.

C. weak force.

D. nuclear force.

#### SOLUTION

Matter consists of elementary charged constituents like electrons and protons. Since the electromagnetic force is so much stronger than the gravitational force, it dominates all phenomena at atomic and molecular scales. The other two forces, i.e., weak forces and nuclear forces, operate only at nuclear scales. Thus it is mainly the electromagnetic force that governs the structure of atoms and molecules, the dynamics of chemical reactions and the mechanical, thermal and other properties of materials.

Q. 113 The branch of Physics that deals with the microscopic domain of physics at the minute scales of atoms and nuclei is called

A. Classical Physics.

B. Quantum physics.

C. Newtonian Physics.

D. Thermal Physics.

#### SOLUTION

Classical and Newtonian Physics deal mainly with macroscopic phenomena and is inadequate to handle macroscopic domain. Quantum physics, on the other hand, deals with the microscopic domain of physics at the minute scales of atoms and nuclei.

Q. 114 The temperature of a bulk system is seen to be related to the average kinetic energy of constituent molecules of the system. This reflects the concept of

A. unification.

B. reductionism.

C. unification and reductionism.

D. deduction.

#### SOLUTION

Attempts have been made to derive the properties of a bigger, more complex, system from the properties and interactions of its constituent simpler parts. This approach is called reductionism.

Q. 115 The nuclear model of an atom was established from

A. the result of experiment of emission of photoelectrons due to photoelectric effect.

B. the result of experiment of Compton scattering.

C. the result of experiment of scattering of alpha particles by gold foil.

D. the result of experiment of nuclear fission reaction taking place in nuclear reactors.

#### SOLUTION

The result of experiment of scattering of alpha particles by gold foil, by Ernest Rutherford established the nuclear model of the atom. It was concluded that there is a massive centre consisting of protons and neutrons and it is surrounded by electrons. The massive centre is known as the nucleus of the atom.

Q. 116 Name the force which have the shortest range?

A. Gravitational forces

B. Nuclear force

C. Electromagnetic force

D. Magnetic force

#### SOLUTION

Nuclear forces have a range of 10-15 m. Gravitational and electromagnetic forces have infinite range.

Q. 117 Cyclotron was discovered by -

A. Newton

B. Yukawa

C. Ernest Orlando Lawrence

D. Edwin Hubble

#### SOLUTION

Ernest Lawrence thought about making a compact accelerator that produced high energy particles. He made one with a circular accelerating chamber between the poles of an electromagnet, which came to be known as cyclotron.

Q. 118 Who discovered the expansion of the Universe?

A. Kelvin

B. Coulomb

C. Rutherford

D. Hubble

#### SOLUTION

Edwin Hubble is known for showing that the recessional velocity of a galaxy increases with its distance from the earth, which implies that the Universe is expanding.

Q. 119 Bhabha lived in -

A. Germany

B. India

C. America

D. Italy

#### SOLUTION

Homi J. Bhabha was born in India on October 30, 1909.

Q. 120 Michelson lived in-

A. Germany

B. Russia

C. America

D. Italy

#### SOLUTION

Michelson was born in Strzelno, Prussian Partition of Poland in 1852. He moved to US in 1855 with his parents.

Q. 121 Who discovered the Nuclear Model of atom?

A. Kelvin

B. Coulomb

C. Rutherford

D. Newton

#### SOLUTION

Rutherford's alpha-ray scattering experiment led to the discovery of atomic nucleus, which led him to postulate the Nuclear model of atom.

Q. 122 Which is not a part of atom -

A.   Electron

B.  Proton

C.  Micron

D.  Neutron

#### SOLUTION

An atom has proton, electron, and neutron only

Q. 123 Who discovered electron?

A. J.J Thomson

B. S.N Bose

C. M.N Saha

D. Edwin Hubble

#### SOLUTION

British physicist, J.J. Thomson discovered electron in 1897.

Q. 124 Who amongst the following have won a Nobel prize?

A. H.J. Bhabha

B. C.V. Raman

C. M.N. Saha

D. S.N. Bose

#### SOLUTION

C.V. Raman won the Nobel prize in 1930 for the discovery of Raman effect.

Q. 125 Which of the following is the weakest force?

A. strong nuclear force

B. gravitational force

C. Electromagnetic force

D. weak nuclear force

#### SOLUTION

force                          relative strength gravitational force                    1 weak nuclear force                  1025 electromagnetic force              1036 strong nuclear forces               1038

Q. 126 Photocell works on the principle of

A. Photoelectric effect

B. Laws of thermodynamics

C. Super conductivity

D. Bernoulli's principle

#### SOLUTION

When light of suitable frequency falls on the emitter of a photocell, it emits electrons on account of photoelectric effect.

Q. 127 What is the major contribution made by Salam?

A. Nuclear modal of atom

B. Theory of relativity

C. Law of gravitation

D. Unification of weak and electromagnetic interaction

#### SOLUTION

Salam, Glashow and Weinberg showed in 1979 that the weak nuclear force and the electromagnetic force can be viewed as different aspects of a single electro-weak force.

Q. 128 Famous theory of relativity was discovered by –

A. Bohr

B. Yukawa

C. Einstein

D. Curie

#### SOLUTION

Albert Einstein gave the special theory of relativity and theory of general relativity.

Q. 129 Read the assertion and reason carefully to mark the correct option out of the options given below.
Assertion: All hypothesis is incorporated into theories.
Reason: Hypothesis are based on scientific observation and experimentations.

A. Assertion is true but reason is false.

B. Assertion and reason both are false.

C. Both assertion and reason are true and the reason is the correct explanation of the assertion.

D. Both assertion and reason are true but reason is not the correct explanation of the assertion.

#### SOLUTION

A hypothesis is an educated guess can either be right or wrong. It has to be tested and proved true, to become a theory.

Q. 130 Read the assertion and reason carefully to mark the correct option out of the options given below.
Assertion: The statement of Newton’s three laws of motion is axiomatic but the statement of universal law of gravitation is a hypothesis.
Reason: The statement which can easily be observed and proved are known as hypothesis while statements which need strong proof are axiomatic.

A. Assertion is true but reason is false.

B. Assertion and reason both are false.

C. Both assertion and reason are true and the reason is the correct explanation of the assertion.

D. Both assertion and reason are true but reason is not the correct explanation of the assertion.

#### SOLUTION

Newton’s laws are axiomatic and can be proved by using logical or mathematical approach. We can easily observe and provide daily life examples to justify the statements of Newton’s laws. However, the universal law of gravitation is a hypothesis, as we cannot prove it using daily life examples.

Q. 131 Neutron was discovered by

A. J.J.Thompson.

C. Albert Einstein.

D. W.Ronentgen.

#### SOLUTION

Q. 132 Electromagnetic forces

A. are central forces.

B. are non-conservative forces.

C. do not obey inverse square law.

D. are short range forces.

#### SOLUTION

Electromagnetic forces are central forces because they act along the line joining the charged particles.

Q. 133 When a bullet is fired from a gun, the gun gains a recoil velocity, which can be determined by using:

A. Law of conservation of energy

B. Law of conservation of mass

C. Law of conservation of momentum

D. Law of conservation of charge

#### SOLUTION

According to law of conservation of momentum, in the absence of an external force, the total momentum of a system remains unchanged. Thus, we can find out the initial momentum of the gun and the bullet before firing and then final momentum after firing. Equating theses two, we can find out the recoil velocity of the gun.

Q. 134 Optic fibres is based on

A. reflection of ultrasonic waves.

B. photoelectric effect.

C. scattering of light.

D. total internal reflection of light.

#### SOLUTION

Optic fibres are used in television. It transmits signals from one place to another by means of total internal reflection of light.

Q. 135 In endothermic reactions, the total binding energy of the reacting molecules is

A. less than the total binding energy of the product molecules

B. greater than the total binding energy of the product molecules

C. equal to the total binding energy of the product molecules

D. converted to the total binding energy of the product molecules

#### SOLUTION

In a chemical reaction, if the total binding energy of the reacting molecules is greater than the total binding energy of the product molecules, the difference is absorbed from the surroundings and the reaction is endothermic.

Q. 136 In exothermic reactions, the total binding energy of the reacting molecules is

A. less than the total binding energy of the product molecules.

B. greater than the total binding energy of the product molecules.

C. equal to the total binding energy of the product molecules.

D. converted to the total binding energy of the product molecules.

#### SOLUTION

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

Q. 137 Isotropy of space underlies

A. the law of conservation of mass.

B. the law of conservation of energy.

C. the law of conservation of linear momentum.

D. the law of conservation of angular momentum.

#### SOLUTION

Isotropy of space signifies that there is no preferred particular direction in space. Hence, it underlies the conservation of angular momentum.

Q. 138 In a nuclear process,

A. mass never gets converted to energy.

B. energy never gets converted to mass.

C. there is inter-conversion of mass and energy.

D. mass gets converted to energy, but the reverse is not possible.

#### SOLUTION

In a nuclear process mass gets converted to energy (or vice-versa). The energy, which is released in a nuclear power generation and nuclear explosions is converted from the mass of the nuclear reactants. An electron and its antiparticle positron can be created from energy (photons).

Q. 139 The quantities which are conserved as well as exists as vectors are

A. total energy and total linear momentum of an isolated system.

B. total linear momentum and total angular momentum of an isolated system.

C. total energy and total angular momentum of any system.

D. total linear momentum and total angular momentum of any system.

#### SOLUTION

The total linear momentum and the total angular momentum of an isolated system are also conserved quantities and both are vectors.

Q. 140 All conserved quantities are

A. not necessarily scalars.

B. necessarily scalars.

C. necessarily vectors.

D. different forms of energy.

#### SOLUTION

Energy is a scalar quantity and is a conserved quantity. But all conserved quantities are not necessarily scalars. The total linear momentum and the total angular momentum of an isolated system are also conserved quantities and both are vectors.

Q. 141 The weak nuclear force is

A. as weak as the gravitational force.

B. much stronger than the strong nuclear and electromagnetic forces.

C. much weaker than the gravitational force .

D. much weaker than the strong nuclear and electromagnetic forces.

#### SOLUTION

The strong nuclear force is the strongest, then comes the electromagnetic force. And the gravitational force is the weakest force. Hence, the weak nuclear force is not as weak as the gravitational force, but much weaker than the strong nuclear and electromagnetic forces.

Q. 142 Protons and neutrons are built out of still more elementary constituents called

A. quarks.

B. electrons.

C. mesons.

D. pions.

#### SOLUTION

Protons and neutrons are built out of still more elementary constituents called quarks. Quarks-Quark force build the universe which caused by the exchnage of particles called gluons is the basic force.

Q. 143 The net force existing between two protons in a nucleus is

A. attractive.

B. repulsive.

C. electrostatic in nature.

D. gravitational in nature.

#### SOLUTION

A nucleus will be unstable only if the electric repulsion between its protons is overcome by some attractive force. This attractive force cannot be gravitational since force of gravity is negligible compared to the electric force. So, this force can be the strong nuclear force, which is the strongest of all fundamental forces. Hence, the net force existing between two protons in a nucleus is attractive.

Q. 144 Strong nuclear force exists between

A. a proton and a neutron only.

B. a proton and a proton only.

C. a neutron and a neutron only.

D. a proton and a proton, a neutron and a neutron, and a proton and a neutron.

#### SOLUTION

The strong nuclear force binds protons and neutrons in a nucleus. It is charge-independent and acts equally between a proton and a proton, a neutron and a neutron, and a proton and a neutron.

Q. 145 Lightning is governed by

A. gravitational forces.

B. electric forces.

C. weak forces.

D. nuclear forces.

#### SOLUTION

The atoms in atmosphere are ionized during the collisions of clouds leading to the production of charged particles. Then electric forces come into play leading to lightning.

Q. 146 Terrestrial phenomena are generally dominated by

A. gravitational forces.

B. electric forces.

C. weak forces.

D. nuclear forces.

#### SOLUTION

Matter is mostly, electrically neutral (net charge is zero). Thus, electric force is largely zero and gravitational force dominates terrestrial phenomena. The other two forces, i.e., weak forces and nuclear forces, operate only at nuclear scales.

Q. 147 Had there been negative masses, gravitational forces would

A. not have existed at all.

B. have been always repulsive.

C. have been always attractive.

D. have been either attractive or repulsive.

#### SOLUTION

Gravity is always attractive because mass comes only in one variety, i.e., there is no negative mass. However, had there been negative masses, gravitational forces would have been either attractive or repulsive as in the case of electric forces where both positive and negative charges exist.

Q. 148 Gravitational

A. and electromagnetic forces do not act over large distances.

B. and electromagnetic need intervening medium.

C. force is enormously strong compared to electromagnetic force.

D. force of the earth is more than that of the moon.

#### SOLUTION

Like the gravitational force, electromagnetic force acts over large distances and does not need any intervening medium. It is enormously strong compared to gravity. The electric force between two protons, for example, is 1036 times the gravitational force between them, for any fixed distance. Since, the mass of the earth is very much greater than that of the moon, its gravitational force is greater.

Q. 149 Who discovered nuclear forces?
A. and electromagnetic forces do not act over large distances.
B. and electromagnetic need intervening medium.
C. force is enormously strong compared to electromagnetic force.
D. force of the earth is more than that of the moon.

#### SOLUTION

H. yukawa

Q. 150 Who proposed the wave theory of light?
A. and electromagnetic forces do not act over large distances.
B. and electromagnetic need intervening medium.
C. force is enormously strong compared to electromagnetic force.
D. force of the earth is more than that of the moon.

#### SOLUTION

Christiaan Huygens

Q. 151 Name the branch of science which deals with study of earth.
A. and electromagnetic forces do not act over large distances.
B. and electromagnetic need intervening medium.
C. force is enormously strong compared to electromagnetic force.
D. force of the earth is more than that of the moon.

#### SOLUTION

Geology.

Q. 152 On which scientific principle does optical fibres work?
A. and electromagnetic forces do not act over large distances.
B. and electromagnetic need intervening medium.
C. force is enormously strong compared to electromagnetic force.
D. force of the earth is more than that of the moon.

#### SOLUTION

Optical fibres work on the principle of total internal reflection of light.

Q. 153 How elastic spring forces arise?
A. and electromagnetic forces do not act over large distances.
B. and electromagnetic need intervening medium.
C. force is enormously strong compared to electromagnetic force.
D. force of the earth is more than that of the moon.

#### SOLUTION

The elastic spring forces arise due to the net attraction / repulsion between the molecules of a spring.

Q. 154 What is physics?
A. and electromagnetic forces do not act over large distances.
B. and electromagnetic need intervening medium.
C. force is enormously strong compared to electromagnetic force.
D. force of the earth is more than that of the moon.

#### SOLUTION

Physics has been taken from Greek word which means nature. Actually many events are taking place in nature in accordance with some basic laws. To reveal those laws with observed events is physics.

Q. 155 Technology is related to physics? Comment on this.
A. and electromagnetic forces do not act over large distances.
B. and electromagnetic need intervening medium.
C. force is enormously strong compared to electromagnetic force.
D. force of the earth is more than that of the moon.

#### SOLUTION

Technological development is closely related to the application of physics. Developed societies always have advanced technologies .Technologists use this information for designing the various appliances and other instruments which help in advancement of physics.

Q. 156 How physics is related to society?
A. and electromagnetic forces do not act over large distances.
B. and electromagnetic need intervening medium.
C. force is enormously strong compared to electromagnetic force.
D. force of the earth is more than that of the moon.

#### SOLUTION

Physics has great impact on society .The discoveries and developments in physics have changed the face of society. Now we have better lifestyle which is because of the inventions in physics like television, radio, and aeroplane.

Q. 157 State various types of forces in nature.
A. and electromagnetic forces do not act over large distances.
B. and electromagnetic need intervening medium.
C. force is enormously strong compared to electromagnetic force.
D. force of the earth is more than that of the moon.

#### SOLUTION

There are mainly four types of forces in nature:

1.      Gravitational force

2.      Nuclear force

3.      Electromagnetic force

4.      Weak force

Q. 158 Name four physical devices widely used in medical diagnosis.
A. and electromagnetic forces do not act over large distances.
B. and electromagnetic need intervening medium.
C. force is enormously strong compared to electromagnetic force.
D. force of the earth is more than that of the moon.

#### SOLUTION

Four physical devices are given as follows:

1. X-Rays tube
2. Electromagnetic resonator (EMR)
3. Stethoscope.
4. Ultrasound machine

Q. 159 Define technology.
A. and electromagnetic forces do not act over large distances.
B. and electromagnetic need intervening medium.
C. force is enormously strong compared to electromagnetic force.
D. force of the earth is more than that of the moon.

#### SOLUTION

It is defined as the study of newest techniques for producing machines, gadgets e.t.c., by using scientific discoveries and advancements.

Q. 160 Name a few war time applications of physics?
A. and electromagnetic forces do not act over large distances.
B. and electromagnetic need intervening medium.
C. force is enormously strong compared to electromagnetic force.
D. force of the earth is more than that of the moon.

#### SOLUTION

The war time application of physics are:
1. Bombs.
2.Nuclear weapons.
3.Jet fighters.
4.Bombers,missile.
5.Transportation and electronic devices.

Q. 161 Name a few maritime applications of physics?
A. and electromagnetic forces do not act over large distances.
B. and electromagnetic need intervening medium.
C. force is enormously strong compared to electromagnetic force.
D. force of the earth is more than that of the moon.

#### SOLUTION

The maritime applications of physics are,
1.Navigation of ships, tankers and aeroplanes.
2.Television.
4.Music System.

Q. 162 Why do we call physics as an exact science?
A. and electromagnetic forces do not act over large distances.
B. and electromagnetic need intervening medium.
C. force is enormously strong compared to electromagnetic force.
D. force of the earth is more than that of the moon.

#### SOLUTION

Physics is called exact science because it involves the accurate measurement of all physical quantities involved.

Q. 163 Name some German Physicists with their contribution.
A. and electromagnetic forces do not act over large distances.
B. and electromagnetic need intervening medium.
C. force is enormously strong compared to electromagnetic force.
D. force of the earth is more than that of the moon.

#### SOLUTION

Some of the famous German Physicists are given as follows:

1.WK Roentgen for: X-Rays.

2.Albert Einstien for: Theory of relativity.

3.H.R Hertz for: Theory of electromagnetic waves.

Q. 164 Read the assertion and reason carefully to mark the correct option out of the options given below.
Assertion: Random error and parallel error comes under the category of personal error.
Reason: Both random error and parallel error arises when a person does not set the apparatus properly and take observations without any precautions.

A. Assertion is true but reason is false.

B. Assertion and reason both are false.

C. Both assertion and reason are true and the reason is the correct explanation of the assertion.

D. Both assertion and reason are true but reason is not the correct explanation of the assertion.

#### SOLUTION

The errors in measurement are broadly classified into two categories. systematic error and random error. Parallax error is a kind of personal error which is a source of systematic error. Parallax error occurs when the observer's eye is not at the proper angle with respect to the scale, which makes the object appear to be at a different position on the scale. Random error arises due to unpredictable fluctuation in the measured data and the precision limitations of the measurement device. Due to random error a person could not find the same measurement in exactly the same way.

Q. 165 Read the assertion and reason carefully to mark the correct option out of the options given below.
Assertion: The Chandrashekar limit is the largest practical length.
Reason: Chandrasekhar limit is approximately 1.4 times the radius of the Sun. A star cannot exist above this limit.

A. Assertion is true but reason is false.

B. Assertion and reason both are false.

C. Both assertion and reason are true and the reason is the correct explanation of the assertion.

D. Both assertion and reason are true but reason is not the correct explanation of the assertion.

#### SOLUTION

Chandrasekhar unit is used for indicating the maximum mass of a white dwarf star which is equivalent to 1.44 solar mass, beyond this limit stars either explode into a supernova or become neutron star or a black hole.

Q. 166 Read the assertion and reason carefully to mark the correct option out of the options given below.
Assertion: The atomic clock cannot give most accurate and precise time in all conditions.
Reason: The reading of the atomic clock can differ as it is based on the frequency and temperature of the sample atom.

A. Assertion is true but reason is false.

B. Assertion and reason both are false.

C. Both assertion and reason are true and the reason is the correct explanation of the assertion.

D. Both assertion and reason are true but reason is not the correct explanation of the assertion.

#### SOLUTION

An atomic clock is a device that measures time by tuning the frequency of microwave wave with the atomic oscillation when they change energy levels. The atomic clocks are so precise and consistent that they would have to run for thousand years before their readings would differ by more than 1 second.

Q. 167 Read the assertion and reason carefully to mark the correct option out of the options given below.
Assertion: The numerical value of the given amount of physical quantity increases if the measuring unit is small and it decreases if unit used is comparatively larger.
Reason: The numerical value and the measuring unit of the physical quantity changes with change in the system of unit.

A. Assertion is true but reason is false.

B. Assertion and reason both are false.

C. Both assertion and reason are true and the reason is the correct explanation of the assertion.

D. Both assertion and reason are true but reason is not the correct explanation of the assertion.

#### SOLUTION

The magnitude of a physical quantity and units are inversely proportional to each other. Larger the unit, smaller will be the magnitude. The product of numerical value and the unit remains constant.

Q. 168 Read the assertion and reason carefully to mark the correct option out of the options given below.
Assertion: Radian is the unit of length.
Reason: Radian is equivalent to the length of the arc which is equal to radius of circle.

A. Assertion is true but reason is false.

B. Assertion and reason both are false.

C. Both assertion and reason are true and the reason is the correct explanation of the assertion.

D. Both assertion and reason are true but reason is not the correct explanation of the assertion.

#### SOLUTION

Radian is an angular unit and is the plane angle subtended by a circular arc at the centre of the circle as the length of the arc divided by the radius of the arc.

Q. 169 1 parsec is

A. 4.26 light years.

B. 3.26 light years.

C. 32.6 light years.

D. 3 light years.

#### SOLUTION

1 light year = 9.46 1015 m. 1 parsec =3.086 1016 m. 1 parsec = [(3.086 1016 m)/(9.46 1015 m)] light years

Q. 170 Length can not be measured in

A. centimeter

B. kilogram

C. meter

D. millimeter

#### SOLUTION

kilogram is the unit of mass.

Q. 171 Which of the following physical quantity denotes the dimension [M1L2T-1]?

A. Surface tension

B. Surface energy

C. Pressure

D. Planck’s constant

#### SOLUTION

A. Surface tension = force/length, dimensions - [M1 L0 T-2] B. surface energy = Potential energy / area, dimensions - [M1 L0 T-2] C. Pressure = force / area, dimensions - [M1 L-1 T-2] D. Planck's constant = energy / frequency, dimensions - [M1 L2 T-1]

Q. 172 The dimension of magnetic dipole moment is

A.  [L2A1]

B. [L2A-1]

C. [L1A-1]

D. [L2A-2]

#### SOLUTION

Magnetic moment =current X area

Q. 173 1 giga meter is equal to

A.  1000 mega meter

B.  100 mega meter

C.  10 mega meter

D. 0.1 mega meter

#### SOLUTION

1 giga meter = 109 meter = 1000 x 106 meter = 1000 mega meter (1 mega meter = 106 meter)

Q. 174 What is the dimension of time in power?

A.  2

B. -2

C. 3

D. -3

#### SOLUTION

Power = work/time = [ML2T-2]/[T]                                = [ML2T-3]

Q. 175 The dimensional formula of tension

A.  [M1L2T-2]

B. [M2L1T-1]

C. [M1L1T-1]

D. [M1L1T-2]

#### SOLUTION

From the tention formula

Q. 176 If x in meter and t in second for the given equation x=at+bt2 dimensions of a is

A. LT-1

B. LT-2

C. LT2

D. LT1

#### SOLUTION

x = at + bt2 Writing the equation in dimensional form, [L ] = a [T] + b [T2] Applying the principle of homogeneity of dimensions, a must have the dimensions of [LT-1].

Q. 177 The dimension equation [ML2T-2] represents

A.  Force

B. Acceleration

C. Energy

D. Pressure

#### SOLUTION

From E=1/2 mv2

Q. 178 If the length and force unit becomes twice then energy unit becomes-

A.  2 times

B. 4 times

C. 8 times

D. 16 times

#### SOLUTION

From the formula E=1/2kx2

Q. 179 The value of 1 joule in erg

A.  100 erg

B. 103 erg

C. 4.38 erg

D. 107 erg

#### SOLUTION Q. 180 If the surface –tension of water is 72 dyne/cm. The value in S.I. Unit-

A.  7.2 Newton/m

B. 720 Newton/m

C. 0.072 Newton/m

D. 0.72 Newton/m

#### SOLUTION

dyne/cm in C.G.S. unit while S.I. is a M.K.S. unit

Q. 181 If the time between two heart beats is Th, time of earth’s revolution is Tre, time of earth’s rotation is Tro, and human life is TL. Write the order of above length-

A.  Tre >Tro>TL>Th

B. Tre >Tro>Th>TL

C. Tro >Tre>TL>Th

D. Th >Tro>Tre>TL

#### SOLUTION

2x109 s>3x107 s>8.6x104 s>1x100 s

Q. 182 Write the order of following length in meters if Radius of earth=Le, The height of the average man=Lm, Thickness of sheet of paper=Lp, The radius of Hydrogen atom=Lh.

A.  Lh>Le>Lm>Lp

B. Lh>Le>Lp>Lm

C. Le>Lm>Lp>L

D. Lp>Le>Lh>Lm

#### SOLUTION

6.4x106 m>1.8x100 m>1x10‑4 m>5x10-11 m

Q. 183 The order of distance travelled by sound in air in 3 second is

A.  104

B. 106

C. 10

D. 108

#### SOLUTION

From velocity of sound in the air =333 m/s
and three second =333.34 x 3= 1000.02= 103 (approx)

Q. 184 How many a.m.u make 1 kg?

A. 0.6 x 1027 a.m.u.

B. 1.6 x 1027 a.m.u.

C. 0.6 x 1025 a.m.u.

D. 1.6 x 1025 a.m.u.

#### SOLUTION

As 1.66 x 10-27 kg = 1 a.m.u., 1 kg = 1/ (1.66 x 10-27) a.m.u. = 0.6 x 1027 a.m.u.

Q. 185 The full form of M.K.S.?

A. Meter kilogram second

B. Meter kilogram centimeter

C. Mole kilogram second

D. Meter gram second

#### SOLUTION

In M.K.S. system of units, metre, kilogram and second are taken as fundamental units of length, mass and time respectively.

Q. 186 What is the unit of Power?

A. Watt

B. Newton

C. Volt

D. Joule

#### SOLUTION

Power = work/ time Unit of Power - J/s (watt)

Q. 187 The order of mass of universe is

A. 1055 kg

B. 1015 kg

C. 1065 kg

D. 1050 kg

#### SOLUTION

Q. 188 Out of the following pairs, which does NOT have identical dimensions ?

A. work and torque

B. moment of inertia and moment of force

C. impulse and momentum

D. angular momentum and Planck's constant

#### SOLUTION

Q. 189 Which of the following statements is wrong about systematic errors?

A. It can be minimized by improving experimental techniques.

B. It can be minimized by selecting better instruments.

C. It can be minimized by removing personal biases.

D. It cannot be minimized.

#### SOLUTION

As the causes of systematic errors are known, these errors can be minimized. The sources of these errors along with the method of their reduction are given below. 1. Instrumental errors - these can be reduced by using more accurate instruments. 2. Imperfection in experimental techniques - these can be reduced by improving experimental techniques. 3. Personal errors - these can be reduced by removing personal errors. 4. Least count error - these can be reduced by using instruments of higher resolution and by improving experimental techniques.

Q. 190 Which of the following pairs have the same dimensions?

A. energy and latent heat

B. light year and time

C. Planck's constant and Wein's constant

D. torque and work

#### SOLUTION

Dimensions of (A) Energy - [M L2 T-2] and Latent heat - [L2 T-2] (B) Light year - [L] and Time - [T] (C) Planck's constant - [M L2 T-1] and Wein's constant - [L K] (D) Torque - [M L2 T-2] and Work - [M L2 T-2]

Q. 191 Each side of the cube is measured to be 7.203 m. The total surface area of the cube appropriate to the significant digits is

A. 234.5m2 .

B. 312.5 m2 .

C. 311.3m2 .

D. 342.5m2 .

#### SOLUTION

The no of significant digits in length is 4. so the area should be rounded off to 4 digits Surface area of cube = 6(7.203)2m2                                   = 311.299254m2                                  =311.3m2

Q. 192 The dimensions of gravitational constant is

A. [M-1L3T-2]

B. [M-2L3T-2]

C. [M-1L2T-2]

D. [M-1L3T-1]

#### SOLUTION

Gravitational force, F = G m1m2/r2 Q. 193 Which of the length measurement is most accurate

A. 500.0 cm.

B. 0.0005 cm.

C. 6.00 cm.

D. 0.0063256 cm

#### SOLUTION

500.0 has 4 significant digits.

Q. 194 A vehicle moving with a speed of 72kmh-1 covers distances in msec-1 equals to

A. 72.

B. 36.

C. 20.

D. 25.

#### SOLUTION Q. 195 The S.I. unit used to express the amount of substance is

A. Atom.

B. Molecule.

C. Electrons.

D. Mole.

#### SOLUTION

The SI unit used to specify amount of substance (or quantity of matter) is mole. One mole is the amount of substance which contains as many elementary entities (atoms, molecules, ions, electrons etc.) as there are atoms in 0.012 kg of pure C12.

Q. 196 If the percentage error in measurements of radius R of sphere is 0.3%.The percentage error in the volume of the sphere will be

A. 0.3%.

B. 0.4%.

C. 0.9%.

D. 0.8%.

#### SOLUTION Q. 197 The sun’s angular diameter is measured to be 1920”.The distance D of the sun from the Earth is 1.496 1011 m.The diameter of the sun will be

A. 2.8 109m.

B. 3.2 109m.

C. 1.39 109m.

D. 2.39 109m.

#### SOLUTION Q. 198 If length,time and energy are fundamental units,then the dimension of mass will be

A. ELT

B. E-2L-3T.

C. EL-1T-2 .

D. EL-2T2 .

#### SOLUTION Q. 199 Light year is a unit of

A. Light

B. Time

C. Distance

D. Mass

#### SOLUTION

Light year is the distance travelled by light in one year in vacuum.

Q. 200 The radius of a solid sphere is measured to be 11.24cm.The surface area of the sphere to appropriate significant figures is

A. 1523 m2 .

B. 1586 cm2 .

C. 15.86 cm2 .

D. 1568 m2 