Category: Engineering Physics Objective Questions

250+ TOP MCQs on Laws of Nature and Answers

Engineering Physics Multiple Choice Questions on “Laws of Nature”.

1. A ship of mass 3×107kg initially at rest is pulled by a force of 5×104N through a distance of 3m. Assuming that the resistance due to water is negligible, the speed of the ship is?
a) 1.5m/s
b) 60m/s
c) 0.1m/s
d) 5m/s
Answer: c
Clarification: a = F/m = (5×104)/(3×107 )
Speed attained by the ship, v = √2as = 0.1m/s.

2. When a bicycle is in motion, the force of friction exerted by the ground on the two wheels is such that, it acts ___________
a) In the backward direction on the front wheel and in the backward direction on the rear wheel
b) In the forward direction on the front wheel and in the backward direction on the rear wheel
c) In the backward direction on both front and the back wheel
d) In the forward direction in both front and the back wheel
Answer: a
Clarification: When a bicycle is in motion, the force of friction acts in the backward direction on the front wheel and in the forward direction on the rear wheel.

3. A weight W rests on a rough horizontal plane. If the angle of friction is θ, the least force that will move the body along the plane will be ___________
a) W cosθ
b) W tanθ
c) W cotθ
d) W sinθ
Answer: b
Clarification: The least force required to move weight W on a horizontal plane is equal to the force of friction, f=μR=μmg or f= W tanθ.

4. Statement 1- A cloth covers a table. Some dishes are kept on it. The cloth can be pulled out without dislodging the dishes from the table.
Statement 2- For every action, there is an equal and opposite reaction.
a) Statement 2 is correct explanation for statement 1
b) Statement 2 is not correct explanation for statement 1
c) Statement 1 is true but statement 2 is false
d) Statement 1 is false but statement 2 is true
Answer: b
Clarification: The dishes will remain on the table due to the inertia of rest and not due to action-reaction forces. Statement 2 is not the correct explanation of statement 1.

5. A player caught a cricket ball of mass 150g moving at a rate of 20m/s. If the ball catching process is completed in 0.1s, the force on the blow exerted by the ball on the hand of the player is equal to ___________
a) 30N
b) 300N
c) 150N
d) 3N
Answer: a
Clarification: Impulse = change in momentum
F = (m(v-u))/t = -30N.

6. A machine gun fires a bullet of mass 40g with a velocity of 1200m/s =. The man holding it can exert a maximum force of 144N on the gun. How many bullets can he fire per second at the most?
a) One
b) Four
c) Two
d) Three
Answer: d
Clarification: Let the maximum number of bullets than can be fired per second be n
Change in momentum of n bullets = nm(v-u) = n×(40(1200-0))/1000 = 48n kgm/s
As impulse = Change in momentum
Ft = 48n
n = Ft/48 = 3bullets/second.

7. A light spring balance hangs from a hook of the other spring balance and a block of mass Mkg hangs from the former one. Then, which of the following is a true statement?
a) Both the scales read Mkg each
b) The scale of the lower one reads Mkg and of the upper one zero
c) The reading of the two scales can be anything but the sum of the readings will be Mkg
d) Both the scales read M/2 kg
Answer: a
Clarification: As the suspended spring balance is lighter one, both the scales will read Mkg each.

8. A particle is acted upon by a force of a constant magnitude which is always perpendicular to the velocity of the particle. The motion of the particle takes place in a plane. It follows that ___________
a) Its velocity is constant
b) Its acceleration is constant
c) Its kinetic energy is constant
d) It moves in a straight line
Answer: c
Clarification: It is a case of uniform motion in which velocity and acceleration vectors change due to change in direction. As the magnitude of velocity remains constant, the kinetic energy is constant.

9. A student unable to answer a question on Newton’s law of motion attempts to pull himself up by tugging on his hair. He will not succeed ___________
a) As the force exerted is small
b) The frictional force while gripping is small
c) Newton’s law of inertia is not applicable to living beings
d) As the force applied is internal to the system
Answer: d
Clarification: The force applied by the student into himself is an internal force. According to Newton’s law, only an external force can change the state of motion of an object.

10. A man of mass 60 kg and a boy of mass 30 kg are standing together on a frictionless ice surface. If they push each other apart, the man moves away with a speed of 0.4m/s relative to ice. After 5s they will be away from each other at a distance of ___________
a) 9 m
b) 3 m
c) 6 m
d) 30 m
Answer: c
Clarification: Momentum of man = -Momentum of boy
60×0.4 = -30×v
Velocity of the boy = -0.8m/s
Relative velocity = 0.4+0.8 = 1.2m/s
Distance between man and boy after 5s = 1.2×5 = 6 m.

250+ TOP MCQs on Moment of Inertia and its Significance and Answers

Engineering Physics Questions and Answers for Aptitude test focuses on “Moment of Inertia and its Significance”.

1. The instantaneous speed of the point of contact during rolling is zero.
a) True
b) False
Answer: a
Clarification: A rolling body can be imagined to be rolling about an axis passing through the point of contact of the body and the ground. Hence the instantaneous speed of the point of contact is zero.

2. A mass m is moving with a constant velocity along a line parallel to the x-axis, away from the origin. Its angular momentum with respect to the origin ___________
a) Is zero
b) Remains constant
c) Goes on increasing
d) Goes on decreasing
Answer: b
Clarification: Angular momentum = Mass of momentum
L = mv×h = constant
As the particle moves, m, v and h all remain unchanged.

3. A particles undergoes uniform circular motion. About which point on the plane of the circle, will the angular momentum of the particles remain conserved?
a) Centre of the circle
b) On the circumference of the circle
c) Inside the circle
d) Outside the circle
Answer: a
Clarification: In uniform circular motion, centripetal force acts towards the centre. Torque due to such a force about the centre is zero. Hence the angular momentum is conserved about the centre of the circle.

4. If the resultant of all the external forces acting on a system of particles is 0, then from an inertial frame, one can surely say that ___________
a) Linear momentum of the system does not change in time
b) Kinetic energy of the system does not change in time
c) Angular momentum of the system does not change in time
d) Potential energy of the system does not change in time
Answer: a
Clarification: According to the law of conservation of linear momentum if external force is 0 then the linear momentum of the system does not change in time. There may be external forces acting due to which kinetic energy or potential energy or both may change. Also, net force is 0 does not mean net torque is 0. So angular momentum may change. Hence only linear momentum of the system does not change in time.

5. Statement 1: If there is no external torque on the body about its centre of mass, then the velocity of the centre of mass remains constant.
Statement 2: The linear momentum of the isolated system remains constant.
a) Statements 1 and 2 are true and statement 2 is the correct explanation of statement 1
b) Statement one and two are true and statement2 is not the correct explanation of statement1
c) Statement 1 is true, statement 2 is false
d) Statement 2 is true, statement 1 is false
Answer: d
Clarification: The absence of external torque does not ensure the absence of external force. If an external force is present, then the velocity of the centre of mass will not remain constant. Thus statement 1 is false.

6. If a person standing on a rotating disc stretches out his hands, the angular speed will ___________
a) Increase
b) Decrease
c) Remains same
d) Increases and then decreases
Answer: b
Clarification: As the person stretches out his hands, his moment of inertia increases. To conserve angular momentum, his angular speed increases.

7. Analogue of mass in rotational motion is ___________
a) Moment of inertia
b) Angular momentum
c) Gyration
d) Angular acceleration
Answer: a
Clarification: Analogue of mass in rotational motion is the angular momentum

8. Moment of inertia of an object does not depend upon ___________
a) Mass of object
b) Mass of distribution
c) Angular velocity
d) Axis of rotation
Answer: c
Clarification: Moment of inertia does not depend on the angular velocity of the object but depends on all factors given in other options.

9. Statement 1: If polar ice melts, days will be longer.
Statement 2: Moment of inertia decreases and thus angular velocity increases.
a) Both statement 1 and 2 are true and statement2 is the correct explanation of the statement1
b) Both statement 1 and 2 are true but the statement2 is not the correct explanation of the statement1
c) Statement 1 is true but statement 2 is false
d) Statement 1 and 2 are false
Answer: a
Clarification: As the polar ice melts, water so formed flows towards the equator. The moment of inertia of the earth increases. To conserve angular momentum, angular velocity decreases. This increases the length of the day.

10. The moment of inertia of a body about a given axis is 1.2kgm2. Initially, the body at rest. In order to produce a rotational kinetic energy of 1500 joule, an angular acceleration of 25radian/sec2 must be applied about the axis for duration of ___________
a) 4s
b) 2s
c) 8s
d) 10s
Answer: b
Clarification: Rotational kinetic energy = 1/2 Iω2
1500=1/2×1.2×ω2
ω=√(3000/1.2)=50rad/s
t=(ω-ω0)/α=(50-0)/25
t=2sec.

Engineering Physics for Aptitude test,

250+ TOP MCQs on Stress and Strain and Answers

Engineering Physics Multiple Choice Questions on “Stress and Strain”.

1. If the stress is S and the Young’s modulus is Y of material of a wire, the energy stored in the wire per unit volume is?
a) 2Y/S
b) S/2Y
c) 2S2 Y
d) S2/ 2Y
Answer: d
Clarification: Elastic potential energy stored per unit volume,
u=1/2×Stress×Strain=1/2×Stress×Stress/Y=S2/2Y.

2. Two wires have the same material and have the same volume. However wire 1 had cross sectional area A and wire 2 has cross sectional area 3A. If the length of wire 1 increases by ∆x on applying force F, how much force is needed to stretch wire 2 by the same amount?
a) F
b) 4F
c) 6F
d) 9F
Answer: d
Clarification: Y=F/A l/∆l=F/A2 Al/∆x=FV/(A2 ∆x)
F=Y∆x/V A2
FαA2
F‘=(3A)2
F‘/F=9
F‘=9F.

3. Amorphous solids are true solids.
a) True
b) False
Answer: b
Clarification: Amorphous solids have disordered arrangement of atoms or molecules. The molecules of the liquid are free to move but the molecules of an amorphous solid are almost fixed at their positions. That is why we say amorphous solids are super-cooled liquids of high velocity.

4. An example of a perfectly plastic body is ___________
a) Quartz
b) Crystal
c) Putty
d) Rubber
Answer: c
Clarification: If on the removal of deforming force, a body does not regain its original configuration even a little, then it is said to be a perfectly plastic body. This putty is a perfectly plastic body.

5. No material is perfectly elastic.
a) True
b) False
Answer: a
Clarification: All materials undergo a change in their original state, howsoever small it may be, after the removal of deforming force. Hence, there is no such material that is perfectly elastic.

6. A given quantity if an ideal gas is at pressure P and absolute temperature T. What is the isothermal bulk modulus of the gas?
a) 2P/3
b) P
c) 3P/2
d) 2P
Answer: b
Clarification: Isothermal bulk modulus of a gas = Pressure of the gas = P.

7. A wire fixed at the upper end stretches by length l by applying a force F. What is the work done in stretching?
a) F/2l
b) Fl
c) 2Fl
d) Fl/2
Answer: d
Clarification: W = 1/2 Stretching force×increase in length
W = 1/2 Fl.

8. The term liquid crystal refers to a state that is intermediate between ___________
a) Crystalline solid and amorphous liquid
b) Crystalline solid and vapour
c) Amorphous liquid and its vapour
d) A crystal immersed in a liquid
Answer: a
Clarification: Liquid crystal is a state intermediate between crystalline solid and amorphous liquid.

9. Which of the following have well defined geometrical external shapes?
a) Amorphous solids
b) Liquids
c) Gases
d) Crystalline solids
Answer: d
Clarification: Crystalline solids have well defined geometrical external shapes because the atoms and molecules are arranged in a definite geometrical repeating manner throughout the body of the crystal.

10. A body of weight mg is hanging on a string that extends in length by l. The work done in extending the string is ___________
a) mgl
b) mgl/2
c) 2mgl
d) 0
Answer: b
Clarification: W=Average force × extension
W=1/2 F×l=1/2 mg×l=mgl/2.

250+ TOP MCQs on Gases and Reactions and Answers

Engineering Physics Multiple Choice Questions on “Gases and Reactions”.

1. In a vessel, the gas at a pressure P. If the mass of all molecules is halved and their speed is doubled, then the resultant pressure will be ___________
a) 4P
b) 2P
c) P
d) P/2
Answer: c
Clarification: According to the kinetic theory of gases, the pressure exerted by a gas,
P=1/3×mn/V v2
P‘/P=2
P‘=2P.

2. The absolute zero is the temperature, at which?
a) All substances exist in a solid state
b) Water freezes
c) Molecular motion ceases
d) Solid melts
Answer: c
Clarification: The absolute zero is the temperature at which all molecular motion ceases.

3. When we heat a gas-sample from 27°C to 327°C, then the initial average kinetic energy of the molecules was E. What will b the average kinetic energy?
a) 327E
b) 300E
c) 2E
d) √2E
Answer: c
Clarification: E‘/E=(273+327)/(273+27)=600/300
E‘=2E.

4. Temperature less than absolute zero is not possible.
a) True
b) False
Answer: a
Clarification: According to the kinetic interpretation of temperature, absolute temperature is proportional to the average kinetic energy of molecules. As the heat is removed, the temperature falls and velocity of molecules decreases. At absolute zero, the kinetic energy becomes zero. As the kinetic energy cannot be negative so no further decrease in kinetic energy is possible. Hence temperature cannot be decreased below absolute zero.

5. A given quantity of an ideal gas at pressure P and absolute temperature T. The isothermal bulk modulus of the gas is ___________
a) 2/3 P
b) P
c) 3/2 P
d) 2P
Answer: a
Clarification: At a given temperature,
P∆V+V∆P=0
P=V∆P/∆V=(∆P/∆V)/V=Isothermal bulk modulus.

6. Statement: The ration Cp/Cv is more for helium gas than that for hydrogen gas.
Reason: Atomic mass of helium is more than that of hydrogen.
a) Both statement and reason are true and the reason is the correct explanation of the statement
b) Both statement and reason are true but the reason is not a correct explanation of the statement
c) Statement it true but the reason is false
d) Both statement and reason are false
Answer: a
Clarification: Both the statement and reason are true but the reason is not a correct explanation of the statement
For monoatomic He,
γ=Cp/Cv = 5/3
For diatomic H2,
γ=Cp/Cv = 7/5.

7. The relation PV=RT can describe behaviour of the real gas at ___________
a) High temperature and high density
b) High temperature and low density
c) Low temperature and low density
d) Low temperature and high density
Answer: b
Clarification: At high temperature and low density, real gas behaves like an ideal gas. Then the intermolecular attractions and actual volume of gas molecules become negligible.

8. An absolute zero is the temperature at which?
a) Water solidifies
b) All gases become liquid
c) rms velocity becomes zero
d) Solids melt
Answer: c
Clarification: According to the kinetic theory of gases, absolute zero is that temperature at which all molecular motion ceases. Hence at T=0K, rms velocity becomes zero.

9. The temperature of a given mass is increased from 27°C to 327°C. The rms velocity of the molecules increases ___________
a) √2 times
b) 2 times
c) 2√2 times
d) 4 times
Answer: a
Clarification: vrms is proportional √T
v2/v1 =√(T2/T1)=√((273+327)/(273+27))=√(600/300)=√2
v2=√2 v1.

10. The ratio of the vapour densities of two gases at a given temperature is 9:8. The ratio of the rms velocities of their molecules is ___________
a) 3:2√2
b) 2√2:3
c) 9:8
d) 8:9
Answer: b
Clarification: At a given temperature,
(vrms (1))/(vrms (2))=√(8/9)=2√2:3.

250+ TOP MCQs on Stationary Waves and Answers

Engineering Physics Multiple Choice Questions on “Stationary Waves”.

1. A train is approaching with velocity 25m/s towards a pedestrian standing on the track, frequency of horn of train is 1 kHz. Frequency heard by the pedestrian is (v=350m/s).
a) 1077Hz
b) 1167Hz
c) 985Hz
d) 945Hz
Answer: a
Clarification: γ‘=v/(v-vs)×γ=350/(350-25)×1000Hz
=1077Hz.

2. A person is standing on a railway platform and a train is approaching to him, what is maximum wavelength of sound he can hear? Wavelength of whistle=1m, speed of sound in air=330m/s, speed of train=36km/h.
a) 1m
b) 32/322m
c) 33/32m
d) 12/13m
Answer: b
Clarification: As γ‘=v/(v-vs)×γ
vs=36km/h=10m/s
ʎ‘=(v-vs)/v×ʎ=(330-10)/330×1=32/33 m.

3. The source of sound generating of a frequency of 3 kHz reaches an observer with a speed of 0.5 times the velocity of sound in air. The frequency heard by the observer is?
a) 1 kHz
b) 3 kHz
c) 4 kHz
d) 6 kHz
Answer: d
Clarification: γ‘=v/(v-vs)×γ
=v/(v-0.5γ)×3kHz=6kHz.

4. A car sounding its horn at 480Hz moves towards a high wall at a speed of 20m/s, the frequency of the reflected sound heard by the man sitting in the car will be nearest to __________
a) 480Hz
b) 510Hz
c) 540Hz
d) 570Hz
Answer: c
Clarification: After reflection from the wall, the sound moves towards observer in the car,
γ‘=(v+v0)/(v-vs)×γ=(340+20)/(340-20)×480=540Hz.

5. A racing car moving towards a cliff sound its horn. The driver observes that the sound reflected from the cliff has a pitch one octave higher than the actual sound of the horn. If v is the velocity of sound, the velocity of the car is?
a) v/√2
b) v/2
c) v/3
d) v/4
Answer: c
Clarification: γ‘/γ=(v+vs)/(v-vs)=2
v+vs=2v-2vs
3vs=v or vs=v/3.

6. If a particle travelling with a speed of 0.9 of the speed of sound and is emitting radiations of frequency if 1kHz and moving towards the observer, what is the apparent frequency?
a) 1.1 kHz
b) 0.8 kHz
c) 0.4 kHz
d) 10 kHz
Answer: d
Clarification: γ‘=v/(v-vs)×γ
=v/(v-0.9v)×1kHz=10kHz.

7. Two trains, each moving with a velocity of 30m/s, cross each other. One of the trains gives a whistle whose frequency is 600Hz. If the speed of sound is 330m/s, the apparent frequency for passengers sitting in the other train before crossing would be __________
a) 600Hz
b) 630Hz
c) 930Hz
d) 720Hz
Answer: d
Clarification: γ‘=v/(v-vs)×γ
=(330+30)/(330-30)×600
360/300×600=720Hz.

8. The phenomenon by which stars recede from each other is explained by __________
a) Black hole theory
b) Neutron star theory
c) White dwarf
d) Red shift
Answer: d
Clarification: Red shift confirms that stars are continuously receding away from each other.

9. Speed of recession of a galaxy is proportional to its distance __________
a) Directly
b) Inversely
c) Exponentially
d) Linearly
Answer: a
Clarification: According to Hubble’s law, the speed of recession (v) of a galaxy is directly proportional to its distance (r) from us.
Where H is Hubble’s constant.

10. The loudness and pitch of a sound note depends on __________
a) Intensity and frequency
b) Frequency and number of harmonics
c) Intensity and velocity
d) Frequency and velocity
Answer: a
Clarification: Loudness depends on intensity while pitch depends on the frequency of sound.

250+ TOP MCQs on Waves and Answers

Engineering Physics Multiple Choice Questions on “Waves”.

1. When a pebble is dropped into a pond of still water, what happens?
a) Particles move
b) Waves move
c) The pebble moves
d) Water moves
Answer: b
Clarification: When a pebble is thrown in still water, a circular pattern of alternate crests spread out. The kinetic energy makes the particles to oscillate which comes in contact with it. The energy gets transferred to the particles of the next layer which also begins to oscillate. Thus it is the disturbance or waves that move forward and not the particles of the medium.

2. Mechanical waves are called elastic waves.
a) True
b) False
Answer: a
Clarification: Waves which require a medium for their propagation are called mechanical waves. They are also called elastic waves because they depend on the elastic properties of a medium.

3. What are the essential properties a medium must possess for the propagation of mechanical waves?
a) Stable pressure
b) Maximum friction
c) Constant temperature
d) Minimum friction
Answer: d
Clarification: The friction force amongst the particles of the medium should be negligibly small so that they continue oscillating for a sufficiently long time and the wave travels a sufficiently long distance through the medium

4. Transverse waves can be formed in fluids.
a) True
b) False
Answer: b
Clarification: Transverse waves travel in the form of crests and troughs. They involve changes in the shape of the medium. So they can be transmitted through media which have rigidity. As fluids do not sustain shearing stress, transverse waves cannot be formed in them.

5. Which of the following waves can be transmitted through solids, liquids and gases?
a) Transverse waves
b) Electromagnetic waves
c) Mechanical waves
d) Longitudinal waves
Answer: d
Clarification: Longitudinal waves involve changes in the volume and density of the medium. Since all media can sustain compressive stress, longitudinal waves can be transmitted through all the three types of media.

6. For an aluminium the modulus of rigidity is 2.1×1010 N/m2 and density is 2.7×103 kg/m3. Find the speed of transverse waves in the medium.
a) 27.9×103 m/s
b) 2.79×103 m/s
c) 25.14×103 m/s
d) 24.1×103 m/s
Answer: b
Clarification: Speed = √(Ƞ/ƿ)
Speed = 2.79×103 m/s.

7. Sound travels through a gas under which of the following condition?
a) Isothermal condition
b) Non-isothermal condition
c) Adiabatic condition
d) Transverse condition
Answer: c
Clarification: The compressions and rarefactions are formed so rapidly that the heat generated in the regions of compressions does not get time to pass into the regions of rarefactions so as to equalize the temperature. So when sound travels through gas, the temperature remains constant. Therefore, it is adiabatic.

8. What kind of wave is formed in organ pipes?
a) Transverse stationary waves
b) Electromagnetic waves
c) Mechanical waves
d) Longitudinal stationary waves
Answer: d
Clarification: When two identical longitudinal waves travelling in opposite directions overlap, a longitudinal stationary wave is formed. Thus, the waves produced in organ pipes are longitudinal stationary waves.

9. A wave transmits momentum. Can’t it transfer angular momentum?
a) Yes
b) No
Answer: b
Clarification: A wave transmitting momentum cannot transmit angular momentum because a transfer of angular momentum means the action of a torque which causes rotator motion.

10. What is the most fundamental property of wave?
a) Temperature
b) Pressure
c) Frequency
d) Wavelength
Answer: c
Clarification: When a wave travels from one medium to other, its wavelength as well as velocity may change. This is the reason that frequency is the fundamental property of a wave.

11. Which of the following is also known as pressure waves?
a) Transverse waves
b) Longitudinal waves
c) Mechanical waves
d) Stationary waves
Answer: b
Clarification: Longitudinal waves travel in a medium as series of alternate compressions and rarefactions and hence are called pressure waves.

12. In which medium sound travels faster?
a) Solid
b) Liquid
c) Gas
d) Water vapour
Answer: a
Clarification: Sound travels in solid with the highest speed because the coefficient of elasticity of solids is much greater than the coefficient of elasticity of liquids and gases.