Category: Engineering Physics Objective Questions

250+ TOP MCQs on Friction and Forces – 3 and Answers

Engineering Physics Interview Questions and Answers for Experienced people focuses on “Friction and Forces – 3”.

1. There is some water in a beaker placed on the pan of a spring balance. If we dip our finger in this water without touching the bottom of the beaker ___________
a) The reading will be the same
b) The reading will increase
c) The reading drops to zero
d) The beaker falls down
Answer: b
Clarification: The water exerts upthrust on the finger and the finger will exert an equal force of reaction on the water in the downward direction. Thus the reading will increase.

2. When a person walks on a rough surface, the frictional force exerted by the surface on the person is opposite to the direction of his motion.
a) True
b) False
Answer: b
Clarification: When a person walks, he pushes the ground backward with his foot. The tendency of the foot when it is in the contact of the earth is to move backward. Hence the force of friction acts in the forward direction.

3. Friction is a non-conservative force.
a) True
b) False
Answer: a
Clarification: When the direction of motion of a body reverses, the direction of friction is also reversed. Work has to be done against both during forward and return journey. So friction is non-conservative force.

4. A stone tied at the end of a string is whirled in a circle. When the string breaks, the stone ___________
a) Falls down vertically
b) Flies upwards
c) Takes a non-uniform path and falls to ground
d) Flies away tangentially
Answer: d
Clarification: The instantaneous velocity of the stone moving round the circle is along the tangent to the circular path. When the string breaks, the centripetal force vanishes. Due to the inertia of motion, the stone flies away tangentially.

5. A Bucket containing water is going in a vertical circle. The water ___________
a) Falls drop by drop
b) Falls all at once
c) Does not fall
d) Only upper half of the water is lost
Answer: c
Clarification: For its revolution in a vertical cycle, water in the bucket needs centripetal force. The weight of the water due to which water can fall is used up in providing the necessary centripetal force and the water does not fall.

6. It is easier to catch a tennis ball than a cricket ball even when both are moving with the same velocity.
a) True
b) False
Answer: a
Clarification: Due to the small mass of tennis ball, the momentum of the table tennis is much smaller than that of the cricket ball of same velocity. Less force is required to stop the table tennis ball than the cricket ball. Hence it is easy to catch the table tennis ball than the cricket ball.

7. The speed of driving a car safely depends on ___________
a) Capacity of the car
b) Fuel in the tank
c) Inflation of tyre
d) Headlight range
Answer: d
Clarification: The driver has to stop the car before it reaches the obstacle. The retarding force acting on the car is constant. If, on applying brakes, the retardation in the car is a, then to stop the car within distance s, the speed v of the cars should be lesser than√2as. Thus the speed of the car depends on the range of the headlight.

8. What is the magnitude of the net force acting a kite skilfully held stationary in the air?
a) Zero
b) Infinity
c) Constant
d) Cannot be predicted
Answer: a
Clarification: As the kite is held stationary, the net force acting on it is zero. The force exerted by the air on the kite is balanced by the tension produced in the string.

9. The driver of a three wheeler with a speed of 36km/h sees a child in the middle of the road and brings his vehicle to rest in 4s just in time to save the child. What is the average retarding force on the vehicle? The mass of the three-wheeler is 400kg and the mass of the driver is 65kg.
a) 116.25 N
b) 2122 N
c) 1162.5 N
d) 212.2 N
Answer: c
Clarification: u = 36km/h=10m/s, v = 0,
t = 4s, m = 400+65kg = 465kg
v=u+at; a = -2.5m/s2
Magnitude of the retarding force on the vehicle is
F = ma = 465×2.5 = 1162.5N.

Engineering Physics for Interviews,

250+ TOP MCQs on Moment of Inertia and Answers

Engineering Physics Multiple Choice Questions on “Moment of Inertia”.

1. A gun fires a bullet of mass 50g with a velocity of 30m/s. Because of this, the gun is pushed back with a velocity of 1m/s. The mass of the gun is?
a) 5.5kg
b) 3.5kg
c) 1.5kg
d) 0.5kg
Answer: c
Clarification: By conservation of momentum, MV = mv
M = mv/V = 1.5kg.

2. A body of mass 5kg is raised vertically to a eight of 10m by a force of 170N. The velocity of the body at this height will be ___________
a) 37m/s
b) 22m/s
c) 15m/s
d) 9.8m/s
Answer: b
Clarification: W = Gain in potential energy+Gain in kinetic energy
Fh = mgh + 1/2 mv2
170×10=5×10×10+1/2×5×v2
v = √480 = 22m/s.

3. A position dependent force, F = 7-2x+3x2-N acts on a small body of mass 2kg and displaces it from x = 0 to x = 5m. The work done in joules is ___________
a) 135
b) 270
c) 35
d) 70
Answer: a
Clarification: W = ∫Fdx = (int_0^5 (7-2x+3x^2)dx = [7x-x^2+x^3]_0^5)
W = 35-25+125=135J.

4. A particle of mass M is moving in a horizontal circle of radius R with uniform speed v. When it moves from one point to a diametrically opposite point, its ___________
a) Kinetic energy changes by (Mv)2/4
b) Momentum does not change
c) Momentum changes by 2Mv
d) Kinetic energy changes by (Mv)2
Answer: c
Clarification: At any two diametrically opposite points, velocities of the particle have the same magnitude but opposite directions. Therefore change in momentum = Mv-(-MV)=2Mv.

5. Two identical balls A and B collide head on elastically. If velocities of A and B, before the collision are +0.5m/s and -0.3m/s respectively, then the velocities after the collision, are ___________
a) -0.5m/s and +0.3m/s
b) +0.5m/s and +0.3m/s
c) +0.3m/s and -0.5m/s
d) -0.3m/s and +0.5m/s
Answer: d
Clarification: In an elastic collision between two bodies of equal masses, velocities get exchanges after collision. vA=-0.3m/s and vB=+0.5m/s.

6. The kinetic energy acquires by a mass m in travelling distance d, starting from rest, under the action of a constant force is directly proportional to ___________
a) m
b) m0
c) √m
d) 1/√m
Answer: b
Clarification: v2-u2=2as
v2-0=2×F/m×d = 2Fd/m
Kinetic energy = 1/2 mv2=1/2 m×2Fd/m = Fd
Hence, kinetic energy does not depend on m or it is directly proportional to m0.

7. A simple pendulum hanging freely and at rest is vertical because in that position ___________
a) Kinetic energy is zero
b) Potential energy is zero
c) Kinetic energy is minimum
d) Potential energy is minimum
Answer: d
Clarification: In the position of equilibrium, the potential energy of the simple pendulum is minimum. Therefore a simple pendulum hanging freely and at rest is vertical because in that position potential energy is minimum.

8. A bullet is fired and gets embedded in a block kept on the table. If a table is frictionless, then ___________
a) Kinetic energy gets conserved
b) Potential energy gets conserved
c) Momentum gets conserved
d) Kinetic energy and potential energy gets conserved
Answer: c
Clarification: Only momentum gets conserved when a bullet is fired and gets embedded in a block kept on a frictionless table. Some kinetic energy is lost when the bullet penetrates the block.

9. A ball moves in a frictionless inclined table without slipping. The work done by the table surface on the ball is ___________
a) Positive
b) Negative
c) Zero
d) Infinity
Answer: c
Clarification: Motion without slipping implies pure rolling. During pure rolling work done by friction force is zero.

10. Assertion: When a body moves along a circular path, no work is done by the centripetal force.
Reason: The centripetal force is used on moving the body along the circular path and hence no work is done.
a) Both assertion and reason are true and reason is the correct explanation of the assertion
b) Both assertion and reason are true but the reason is not the correct explanation of assertion
c) Assertion is true but reason is false
d) Both assertion and reason are false
Answer: c
Clarification: The assertion is true but the reason is false. The work done by the centripetal force is zero because it acts perpendicular to the circular path.

250+ TOP MCQs on Elastic Limit and Answers

Engineering Physics Multiple Choice Questions on “Elastic Limit”.

1. Amorphous solids do not melt at a sharp temperature, rather these have softening range.
a) True
b) False
Answer: a
Clarification: All bonds in an amorphous solid are not equally strong. When then solid is heated, weaker bonds gets ruptured at the lowest temperature and the stronger ones at higher temperatures. So the solid first softens and then finally melts.

2. Which is more elastic?
a) Water
b) Air
c) Solid
d) Crystal
Answer: a
Clarification: Water is more elastic than anything else. Air can be compressed easily whereas water is incompressible and bulk modulus is reciprocal of compressibility.

3. The following wires are made of the same material. Which of these will have the largest extension, when the same tension is applied?
a) Length = 50cm, diameter = 0.5mm
b) Length = 100cm, diameter = 1mm
c) Length = 200cm, diameter = 2mm
d) Length = 300cm, diameter = 3mm
Answer: a
Clarification: ∆l=F/A l/Y=4F/(πD2) l/Y
In Length = 50cm, diameter = 0.5mm, l/D2 = 50/0.052 = 2×104 cm-1
In Length = 100cm, diameter = 1mm, l/D2 = 100/0.12 = 104 cm-1
In Length = 200cm, diameter = 2mm, l/D2 = 200/0.22 = 5×103 cm-1
In Length = 300cm, diameter = 3mm, l/D2 = 300/0.32 = 3.3×103 cm-1
Hence ∆l is maximum in Length = 50cm, diameter = 0.5mm.

4. There are two wires of same material and same length while the diameter of second wire is two times the diameter of first wire, then the ratio of extension the diameter of first wire, then the ratio of extension produced in the wire by applying same load will be _____________
a) 1:1
b) 2:1
c) 1:2
d) 4:1
Answer: d
Clarification: Extension,
∆l=F/A l/Y=F/(πr2) l/Y
For the two wires F, l and Y are same, so
(∆l1)/(∆l2)=((r2)2)/((r1)2)=(2/1)2 4:1.

5. A cube is subjected to a uniform volume compression. If the side of the cube decreases by 2%, the bulk strain is ___________
a) 0.02
b) 0.03
c) 0.04
d) 0.06
Answer: d
Clarification: V=l3
∆V/V=3∆l/l=3(2/10)=0.06.

6. Energy stored in stretching a string per unit volume is ___________
a) 1/2×stress×strain
b) stress×strain
c) Y(Strain)2
d) 1/2 Y(Stress)2
Answer: a
Clarification: Energy stored per unit volume= Work done per unit volume
Energy stored per unit volume = 1/2×Stress×strain.

7. According to Hooke’s law of elasticity, if stress is increased, the ratio of stress to strain?
a) Increased
b) Decreased
c) Becomes zero
d) Remains constant
Answer: d
Clarification: According to Hooke’s law,
Stress/Strain=constant.

8. If in a wire of Young’s modulus Y, longitudinal strain is produced, then the value of potential energy stored in its unit volume will be ___________
a) YX2
b) 0.5Y2 X
c) 2YX2
d) 0.5YX2
Answer: d
Clarification: Potential energy stored per unit volume,
u=1/2×Stress×Strain=1/2 (Y×Strain)×Strain
u=0.5YX2.

9. A stretched rubber has ___________
a) Increased kinetic energy
b) Increased potential energy
c) Decreased kinetic energy
d) Decreased potential energy
Answer: b
Clarification: The work done in stretching the rubber is stored as its potential energy.

10. The breaking stress of a wire depends upon ___________
a) Length of the wire
b) Radius of the wire
c) Material of the wire
d) Shape of the cross-section
Answer: c
Clarification: The stress at which rupture of the wire occurs is called its breaking stress. Its value depends on the material of the wire.

11. Which of the following affects the elasticity of a substance?
a) Hammering and annealing
b) Change in temperature
c) Impurity in substance
d) All of the mentioned
Answer: d
Clarification: All the factors change in temperature, hammering and annealing and impurity in substance affects the elasticity of a substance.

12. The diameter of brass rod is 4mm. Young’s modulus of brass is 9×109 N/m2. The force required to stretch 0.1% of its length is ___________
a) 360πN
b) 36N
c) 36π×105 N
d) 144π×103N
Answer: a
Clarification: ∆l/l=0.1/100
F=YA∆l/l=(Y×πr2×∆l)/l
F=(9×109×π×(2×10(-3))2×0.1)/100 N=360πN.

13. A substance breaks down by a stress of (106 N)/m2. If the density of the material of the wire is 3×(103) kg/m3, then the length of the wire of the substance which will break under its own weight when suspended vertically will be ___________
a) 66.6m
b) 60.0m
c) 33.3m
d) 30.3m
Answer: c
Clarification: Breaking stress = mg/area=Alρg/A=lρg
l=Stress/ρg=106/(3×103×10)=33.3m.

250+ TOP MCQs on Ideal Gases – 2 and Answers

Engineering Physics Quiz focuses on “Ideal Gases – 2”.

1. In the upper part of the atmosphere, the kinetic temperature of the air is of the order 1000K. Therefore one feels extremely hot.
a) True
b) False
Answer: b
Clarification: As we go up the atmosphere, the number of air molecules per unit volume decreases. The quantity oh heat per unit volume or the heat density is low. But the translational kinetic energy per molecule is quite large. As the kinetic temperature is the measure of translational kinetic energy, so the kinetic temperature is quite high in the upper atmosphere but one feels severe cold there due to low density.

2. What type of motion is associated with the molecules of gas?
a) Newton’s law of motion
b) Conservative motion
c) Linear motion
d) Brownian motion
Answer: d
Clarification: Brownian motion is associated with the molecules of a gas. In this motion, any particular molecule will follow a zigzag path due to the collisions with the other molecules or with the walls of the container.

3. At room temperature, the rms speed of the molecules of a certain diatomic gas is found to be 1920ms-1. Which is the gas?
a) H2
b) F2
c) O2
d) Cl2
Answer: a
Clarification: vrms=√(3RT/M)
M=3RT/(vrms)2 = (3×8.3×300)/(1920)2 = 2
Hence the gas is H2.

4. A vessel contains a mixture of 1 mole of oxygen and 2 moles of nitrogen at 300 K. The ratio of the average rotational kinetic energy per O2 molecule to that per N2 molecule is?
a) 1:1
b) 1: 2
c) 2:1
d) Depends on the moment of inertia of the two molecules
Answer: d
Clarification: Both gases are diatomic. Both have two rotational degrees of freedom at 300K. Average rotational kinetic energy per molecule of each gas will be same=2×1/2 kT=1kT
Hence the required ratio is 1:1.

5. Statement: For an ideal gas at constant temperature, the product of the pressure and volume is a constant.
Reason: The mean square velocity of the molecules is inversely proportional to mass.
a) Both statement and reason are true and explanation is the correct explanation of the statement
b) Both statement and reason are true but the explanation 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: b
Clarification: Both the statement and reason are true but the explanation is not a correct explanation of the statement. According to Boyle’s law, PV=constant, at a given temperature.

6. An ant is walking on the horizontal surface. The number of degrees of freedom of ant will be ___________
a) 1
b) 2
c) 3
d) 6
Answer: b
Clarification: As the ant can move on a plane, it has 2 degrees of freedom.

7. The number of degrees of freedom for a diatomic gas molecule is ___________
a) 2
b) 3
c) 5
d) 6
Answer: c
Clarification: A diatomic molecule has 3 degrees of freedom due to translator motion and 2 degrees of motion due to rotator motion.

8. A gas at one atmosphere and having volume 100ml is mixed with another gas of equal moles at 0.5atm and having volume 50ml in flask of one litre, what is the final pressure?
a) 0.5atm
b) 1atm
c) 0.75atm
d) 0.125atm
Answer: d
Clarification: Total number of moles is conserved.
(P1 V1)/RT+(P2 V2)/RT=PV/RT
(1×100)/RT+(0.5×50)/RT=(P×1000)/RT
P=0.125atm.

9. Temperature of oxygen kept in a vessel is raised by 1°C at constant volume. Heat supplied to the gas may be taken partly as translational and partly rotational kinetic energies. Their respective shares are ___________
a) 60%, 40%
b) 50%, 50%
c) 100%, zero
d) 40%, 60%
Answer: a
Clarification: A diatomic oxygen molecule has 3 degrees of freedom due to translator motion and 2 degrees of freedom due to rotator motion. Their associated kinetic energies will be in the ratio 3:2 or 60% and 40%.

10. An ideal gas is heated from 27°C to 627°C at constant pressure. If initial volume was 4m3, then the final volume of the gas will be?
a) 2m3
b) 4m3
c) 6m3
d) 12m3
Answer: d
Clarification: Using Charle’s law,
V1/T1 = V2/T2
V2=T2/T1 ×V1=((273+627))/((273+27))×4=900/300×4=12m3.

Engineering Physics for Quizzes,

250+ TOP MCQs on Travelling Waves and Answers

Engineering Physics Multiple Choice Questions on “Travelling Waves”.

1. When the length of the vibrating segment of a sonometer wire is increased by 1%, the percentage change in its frequency is?
a) 100/101
b) 99/100
c) 1
d) 2
Answer: c
Clarification: v=1/2L×√(T/m)
For constant T and m,
∆v/v×100=∆L/L×100=1%
Frequency will decrease by 1%.

2. In an experiment with sonometer a tuning fork of frequency 256Hz resonates with a length of 25cm and another tuning fork resonates with a length of 16xcm. Tension of the spring remaining constant the frequency of the second tuning fork is?
a) 163.84Hz
b) 400Hz
c) 320Hz
d) 20.4Hz
Answer: b
Clarification: v∝1/L
v2/v1 = L1/L2
v2=L1/L2 ×v1=25/16×256=400Hz.

3. An open pipe resonates with a tuning fork of frequency 500Hz. It is observed that two successive nodes are formed at distances 16 and 46cm from the open end. The speed of sound in air in the pipe is?
a) 230 m/s
b) 300 m/s
c) 320 m/s
d) 360 m/s
Answer: b
Clarification: v=2γ(l2-l1)
v=2×500(46-16)cm/s
=30000cm/s=300m/s.

4. The velocity of sound in open ended tube in 330m/s, the frequency of a wave is 1.1 kHz and length of the tube is 30cm, then number of harmonics that it will emit is?
a) 2
b) 3
c) 4
d) 5
Answer: a
Clarification: For an open tube,
vn=nv/2L
1.1×103=(n×330)/(2×0.30)
n=2.

5. An organ pipe, open at both ends produce 5 beats per second when vibrated with a source of frequency 200Hz. The second harmonic of the same pipe produces 10 beats per second with a source of frequency 420 Hz. The frequency of source is?
a) 195Hz
b) 205Hz
c) 190Hz
d) 210Hz
Answer: b
Clarification: Fundamental frequency of open pipe,
f=200±5=195Hz or 205Hz
Second harmonics of open pipe,
2f=420±10=410Hz or 430Hz
f=205Hz or 215Hz.

6. Following two wave trains are approaching each other
y1=asin200πt, y2=asin208πt.
The number of beats heard per second is?
a) 8
b) 4
c) 1
d) Zero
Answer: b
Clarification: ω1=2πv1=200π or v1=100Hz
ω2=2πv2=208π or v2=105Hz
Beat frequency=v2-v1=4Hz.

7. Two waves of wavelength 99cm and 100cm both travelling with velocity 396m/s are made to interfere. The number of beats produced by them per second is?
a) 1
b) 2
c) 4
d) 8
Answer: c
Clarification: Beat frequency=v[(1/ʎ1)-(1/ʎ2)]
=396[(1/0.99)-(1/1)]=4Hz.

8. Two waves are propagating with the same amplitude and nearly same frequency in opposite direction, they result in __________
a) Beats
b) Stationary wave
c) Resonance
d) Wave packet
Answer: b
Clarification: Stationary waves are formed when two waves of same frequency travelling in opposite directions are superimposed.

9. A tuning fork A produces 4beats/s with another tuning fork B of frequency 320Hz. On filing one of the prongs of A, 4beats/s is again heard when sounded with the same fork B. Then, the frequency of the fork A before filing is __________
a) 328Hz
b) 316Hz
c) 324Hz
d) 320Hz
Answer: b
Clarification: Frequency of A=320±4=324 or 316Hz. As frequency increases on filing, so frequency of A=316Hz (lower value).

10. A source emits a sound of a frequency of 400Hz, but the listener hears it’s to be 390Hz. Then?
a) The listener is moving towards the source
b) The source is moving towards the listener
c) The listener is moving away from the source
d) The listener has a defective ear
Answer: c
Clarification: As apparent frequency is lesser than the actual frequency, the listener is moving away from the source.

250+ TOP MCQs on Compton Effect and Answers

Engineering Physics Multiple Choice Questions on “Compton Effect”.

1. Which of the following is the characteristic of a black body?
a) A perfect absorber but an imperfect radiator
b) A perfect radiator but an imperfect absorber
c) A perfect radiator and a perfect absorber
d) A perfect conductor
Answer: c
Clarification: When the radiations are made to pass through a black body, it undergoes multiple reflections and is completely absorbed. When it is placed in a temperature bath of fixed temperature, the heat radiations will come out. Thus a black body is a perfect absorber and a perfect reflector.

2. The energy distribution is not uniform for any given temperature in a perfect black body.
a) True
b) False
Answer: a
Clarification: At different temperatures, when a perfect black body is allowed to emit radiations, then the distribution of energy for different wavelengths at various temperatures is not uniform.

3. Rayleigh-Jean’s law holds good for which of the following?
a) Shorter wavelength
b) Longer wavelength
c) High temperature
d) High energy
Answer: b
Clarification: According to this law, the energy distribution is directly proportional to the absolute temperature and is inversely proportional to the fourth power of the wavelength. Therefore longer the wavelength, greater is the energy distribution.

4. Wien’s displacement law holds good only for shorter wavelength.
a) False
b) True
Answer: b
Clarification: This law states that, the product of the wavelength, corresponding to maximum energy and the absolute temperature, is constant. If ʎ is less, then 1/ʎ will be great. Therefore e(hc/ʎKT) will be great.

5. Which of the following does not affect the photon?
a) Magnetic or electric field
b) Light waves
c) Gravity
d) Current
Answer: a
Clarification: Photons have no charge. They can interact with charged particles but not with themselves. This is why photons are neutral and not affected by magnetic or electric fields.

6. What is Compton shift?
a) Shift in frequency
b) Shift in charges
c) Shift in radiation
d) Shift in wavelength
Answer: d
Clarification: When a photon collides with an electron at rest, the photon gives its energy to the electron. Therefore the scattered photon will have higher wavelength compared to the wavelength of the incident photon. This shift in wavelength is called Compton shift.

7. Compton shift depends on which of the following?
a) Incident radiation
b) Nature of scattering substance
c) Angle of scattering
d) Amplitude of frequency
Answer: c
Clarification: From the theory of Compton effect it is deducted that change in wavelength
Δʎ = h/mc (1-cosɵ). This equation shows that the change in wavelength is independent of the incident radiation as well as the nature of scattering substance. The shift depends only on the angle of scattering.

8. Which of the following is called as non-mechanical waves?
a) Magnetic waves
b) Electromagnetic waves
c) Electrical waves
d) Matter waves
Answer: b
Clarification: The waves which travel in the form of oscillating electric and magnetic waves are called electromagnetic waves. Such waves do not require any material for their propagation and are called non-mechanical waves.

9. Which of the following is associated with an electron microscope?
a) Matter waves
b) Electrical waves
c) Magnetic waves
d) Electromagnetic waves
Answer: a
Clarification: The waves associated with microscopic particles when they are in motion are called matter waves. Electron microscope makes use of the matter waves associated with fast moving electrons.

10. A radio station broadcasts its programme at 219.3 metre wavelength. Determine the frequency of radio waves if velocity of radio waves is 3×108 m/s.
a) 7.31×10-7 Hz
b) 1.954×10-6 Hz
c) 1.368×106 Hz
d) 6.579×1010 Hz
Answer: c
Clarification: ʎ = velocity/frequency
Frequency = velocity/ʎ
Therefore, frequency = 1.368×106 Hz.

11. Calculate the de-Broglie wavelength of an electron which has been accelerated from rest on application of potential of 400volts.
a) 0.1653 Å
b) 0.5125 Å
c) 0.6135 Å
d) 0.2514 Å
Answer: c
Clarification: de-Broglie wavelength = h/√(2×m×e×V)
De-Broglie wavelength = (6.625×10-14)/√(2×9.11×10-31×1.6×10-19×400)
Wavelength = 0.6135 Å.