Multiple choice question for engineering
Set 1
1. What is the science that deals with every substance, its structure, its composition and changes?
a) Botanical science
b) Zoological science
c) Chemistry
d) Physics
Answer
Answer: c [Reason:] Chemistry is the science that deals with every substance, its structure, its composition and changes. Physics is the study of natural world, matter, energy and radiation, while biology is the science that deals with the behaviour of living things are called biological sciences.
2. Quantum physics deals with macroscopic phenomena. True or false?
a) True
b) False
Answer
Answer: b [Reason:] Classical physics deals with macroscopic phenomena which may be at the laboratory, terrestrial and astronomical. Quantum physics deals with microscopic phenomena at the minute scales of atoms.
3. Which of the following use electromagnetic waves?
a) Radio
b) Radiotherapy
c) Detecting fractures
d) Electric motors
Answer
Answer: a [Reason:] Electromagnetic waves are used in radio. While radiotherapy and detecting fractures are done by x-rays and electric motor comes under electric appliance.
4. Which is the universal attractive force?
a) Electromagnetic force
b) Strong nuclear force
c) Weak nuclear force
d) Gravitational force
Answer
Answer: d [Reason:] Gravitational force is the force of mutual attraction between two bodies by virtue of their masses. Every body attracts every other body in the universe with this force. Hence it is the universal attractive force.
5. Gravitational force is the weakest force in nature. True or false?
a) True
b) False
Answer
Answer: a [Reason:] Gravitational force is the weakest force in nature because it cannot be felt by us in daily basis. Electromagnetic force is the strongest force in nature.
6. Which of the following is an example for electromagnetic force?
a) Motion of moon around earth
b) Evolution of stars
c) Evolution of galaxies
d) Compression of spring
Answer
Answer: d [Reason:] When a spring is compressed, it exerts a force of elasticity due to the net repulsion/ attraction between the neighbouring atoms. This net repulsion or attraction is the sum of the electrostatic forces between the electrons and nuclei of the atoms.
7. Why is climbing a lamp post harder than climbing up a tree?
a) Because of parallel friction force
b) Because of contact force between the bodies
c) Because of Van der Wall’s force
d) Because of rope force
Answer
Answer: a [Reason:] Sometimes, the electromagnetic contact force between two bodies may have a component acting parallel to the surface of contact. This is called friction. When bodies are placed with their smooth surfaces in contact, they provide only a small parallel component of contact of force and hence friction between them is small. This is why climbing a metallic lamp post is difficult than climbing up a tree.
8. Gravitational force, despite being a weak force, governs the large scale motion. True or false?
a) True
b) False
Answer
Answer: a [Reason:] Mass is only of one type. So the gravitational force is always attractive. Between two neutral objects, the gravitational force goes on adding over all pairs of particles of the two objects while the electromagnetic forces being equally attractive and repulsive, add up to zero. That is why large scale motion in the universe is controlled by the weakest gravitational force.
9. When a body is falling freely under gravity, the total mechanical energy remains constant because of which of the following?
a) Law of conservation of energy
b) Unification of force
c) Electromagnetic force
d) Gravity
Answer
Answer: a [Reason:] According to law of conservation of energy, energy can neither be created nor can it be destroyed but it can be changed from one form to another. When a body is falls freely, under gravity, its potential energy gradually changes into kinetic energy. But its total mechanical energy remains constant at any point of its motion.
10. What happens when a bullet is fired from rifle?
a) The rifle becomes weightless
b) We fall back
c) Rifle gives backward kick
d) Bullet doesn’t leave the rifle
Answer
Answer: c [Reason:] A rifle gives a backward kick on firing a bullet. Before firing, both the bullet and rifle are at rest and initial momentum of the system is zero. As soon as bullet is fired, it moves forward with a large velocity. In order to conserve momentum, the rifle moves backward with such a velocity that the final momentum of the system is zero.
Set 2
1. Which of the following is used for measuring long time intervals?
a) Electrical oscillators
b) Atomic clocks
c) Decay of elementary particles
d) Radioactive dating
Answer
Answer: d [Reason:] Radioactive dating is used to measure long time intervals by finding the ratio of the number of radioactive atoms that have undergone decay to the number of atoms left undecayed. Carbon dating is used to estimate the age of fossils, uranium dating is used to estimate the age of rocks.
2. The average life of an Indian is 56 years. Find the number of times the human heart beats in the life of an Indian, if the heat beats once in 0.8 s.
a) 20.4×109 times
b) 2.5×109 times
c) 2.2×109 times
d) 6.1×109 times
Answer
Answer: c [Reason:]
Average life of an Indian = 56 years = 56×365.25×24×60×60 s
Period of heart beat = 0.8 s
Total number of heart beats in 56 years = (56×365.25×24×60×60)/0.8 = 2.2×109 times
3. How many dimensions of world is there?
a) 7
b) 3
c) 2
d) 4
Answer
Answer: a [Reason:] All the derived quantities can be expressed in terms of some combination of the seven fundamental or base quantities. We call these seven fundamental quantities as the seven dimensions of the world.
4. What is the dimensional formula for Gravitational constant?
a) ML2 T(-3)
b) ML(-1) T(-2)
c) ML(-1) T(-1)
d) M(-1) L3 T(-2)
Answer
Answer: d [Reason:] F = G(m1 m2)/r2
G = ([F][r2])/([m1 ][m2]) = (MLT(-2) L2)/MM = M(-1) L3 T(-2)
5. Which of the following is a dimensional constant?
a) e
b) Area
c) Specific gravity
d) Gravitational constant
Answer
Answer: d [Reason:] The physical quantities which posses dimensions and have constant values are called dimensional constants. Hence Gravitational constant is a dimensional constant.
6. If the unit of force is 1kN, unit of length 1km and the unit of time is 100s, what will be the unit of mass?
a) 1000 kg
b) 104 kg
c) 100 kg
d) 105 kg
Answer
Answer: b [Reason:] M = (MLT(-2) T2)/L = (FT2)/L
M = (1000 N ×104 s2)/(1000 m) =104 kg
7. Which of the following is systematic error?
a) Constant error
b) Least count error
c) Gross error
d) Personal error
Answer
Answer: d [Reason:] The errors which occur in one direction, either positive or negative, are called systematic error. Personal errors arise due to improper setting of instruments. Hence it comes under systematic error.
8. All physical quantities have dimensions. True or false?
a) True
b) False
Answer
Answer: b [Reason:] All physical quantities do not have dimensions. Like angle, strain and relative density are examples for dimension less quantity.
9. An instrument cannot be precise without being accurate. True or false?
a) False
b) True
Answer
Answer: a [Reason:] An instrument can be precise without being accurate but the instrument cannot be accurate without being precise.
10. Can the diameter of thread be measure by using a scale?
a) Yes
b) No
Answer
Answer: a [Reason:] The thread is wound on a meter scale such that its turns are close together. Thickness of the thread coil is measure and the number of turn made by the thread is counted. Diameter is then given by dividing the thickness by number of turns.
11. Calculate the de-Broglie wavelength of an electron which has been accelerated from rest on application of potential of 400volts.
a) 0.1653 Amstrong
b) 0.5125 Amstrong
c) 0.6135 Amstrong
d) 0.2514 Amstrong
Answer
Answer: c [Reason:] 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 Amstrong
Set 3
1. A body of mass 0.25kg moving with a velocity 12m/s is stopped by applying a force of 0.6N. Calculate the time taken to stop the body.
a) 24s
b) 5s
c) 3s
d) 7s
Answer
Answer: b [Reason:] m = .25kg, u = 12m/s, v = 0, F = -0.6N
a = F/m = 0.6/0.25 = -24m/s2
t = (v-u)/a = (0-12)/(-24) = 5s
2. Action and reaction takes place on the same bodies. True or false?
a) True
b) False
Answer
Answer: b [Reason:] If the action an reaction were on the same body, the resultant force would be zero and there could never be accelerated motion. Therefore, action and reaction always act on different bodies.
3. Which of the following is the property of Newton’s third law?
a) A body moving with a uniform speed in a straight line cannot change the direction of motion by itself
b) It is applicable only to a point particle
c) It is a local relation
d) The action and reaction cannot cancel each other
Answer
Answer: d [Reason:] The forces of action and reaction cannot cancel each other. This is because action and reaction, although equal and opposite, always act on different bodies and so cannot balance each other.
4. Book kept on a table is an example for
a) Inertia
b) First law of motion
c) Third law of motion
d) Second law of motion
Answer
Answer: c [Reason:] The book exerts a downward force on the table equal to its own weight. According to Newton’s third law, the table also exerts an equal and upward force on the book. As the book is under the action of two equal and opposite forces, it remains in equilibrium.
5. Which of the following is called real law of motion?
a) Second law
b) First law
c) Third law
d) Law of inertia
Answer
Answer: a [Reason:] First law is contained in the second law: In the absence of external force a body at rest will remain at rest and a body in motion will continue to move. Third law is contained in the second law: In the absence of external force, the rate of change of momentum must be zero. This is third law of motion. As both first and second law are confine in the second law, it the real law of motion.
6. For a man standing inside a life, when will his apparent weight be equal to real weigh?
a) When the life is moving upwards with a uniform acceleration
b) When the lift is moving downwards with a uniform velocity
c) At rest or moving with uniform velocity
d) Falling freely
Answer
Answer: c [Reason:] When the life is in rest or moving with a uniform velocity, the acceleration = 0. Net force on the man is zero. Therefore apparent weight will be equal to real weight of the man.
7. Conservation of linear momentum is a combination of
a) Newton’s second law and third law
b) Newton’s second law and first law
c) Newton’s first law and third law
d) Newton’s second law and impulse force
Answer
Answer: a [Reason:] The second and third law of motion leads to one of the most important and fundamental principles of physics called law of conservation of momentum. When no external force acts on a body, the total linear momentum is conserved.
8. While firing a bullet, the gun should be
a) Held away from the shoulder
b) Held tight to the shoulder
c) Held straight
d) Held with one hand stretched
Answer
Answer: b [Reason:] While firing a bullet, the gun should be held tight to the shoulder. The recoiling can hurt the shoulder. If the gun is held tightly against the shoulder, then the body and the gun together will constitute one system. Total mass becomes larger and the recoil velocity becomes small.
9. When a man jumps out of a boat to the shore, the boat slightly moves away from the shore. True or false?
a) True
b) False
Answer
Answer: a [Reason:] Initially, the total momentum of the boat and the man is zero. As the man jumps from the boat to the shore, he gains a momentum in the forward direction. To conserve momentum, the boat also gains an equal momentum in the opposite direction. So the boat slightly moves backwards.
10. A man weighing 60kg runs along the rails with a velocity of 18km/h and jumps into a car of mass 1 quintal standing on the rails. Calculate the velocity with which the car will start travelling along the rails.
a) 15m/s
b) 3.3m/s
c) 1.88m/s
d) 5m/s
Answer
Answer: c [Reason:] m1 = 60kg, u1 = 18km/h = 5m/s
m2 = 1quintal = 100kg, u2 = 0, v = ?
By conservation of linear momentum, (m1+m2)v = m1 u1+m2 u2
v = (60×5)/160 = 1.88m/s
11. Fuel is consumes at the rate of 100kg/s in a rocket. The exhaust gases are ejected at speed of 4.5×104m/s. What is the thrust experienced by the rocket?
a) 3.19×106N
b) 4.5N
c) 3.19N
d) 4.5×106N
Answer
Answer: d [Reason:] dm/dt = 100kg/s, u = 4.5×104m/s
Thrust, F = udm/st = 4.5×104×100 = 4.5×106N
Set 4
1. Amorphous solids do not melt at a sharp temperature, rather these have softening range. True or false?
a) True
b) False
Answer
Answer: a [Reason:] All bonds in an amorphous solid are not equally strong. When then solid is heated, weaker bonds gets ruptured at 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
Answer: a [Reason:] 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
Answer: a [Reason:] ∆l=F/A l/Y=4F/(πD2 ) l/Y
In a, l/D2 =50/0.052 =2×104 cm-1
In b, l/D2 = 100/0.12 =104 cm-1
In c, l/D2 = 200/0.22 =5×103 cm-1
In d, l/D2 = 300/0.32 =3.3×103 cm-1
Hence ∆l is maximum in a
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
Answer: d [Reason:] 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
Answer: d [Reason:] 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
Answer: a [Reason:] From the above problem,
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
Answer: d [Reason:] 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
Answer: d [Reason:] 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
Answer: b [Reason:] 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
Answer: c [Reason:] 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
Answer: d [Reason:] All the factors change in temperature, hammering and annealing and impurity in substance affect 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
Answer: a [Reason:] ∆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
Answer: c [Reason:] Breaking stress = mg/area=Alρg/A=lρg
l=Stress/ρg=106/(3×103×10)=33.3m
Set 5
1. When too many people stand on a bridge it collapses, why?
a) Due to increase in stress
b) Due to overweight
c) Due to improper construction
d) Due to friction
Answer
Answer: a [Reason:] Stress is the force per unit area experienced by the body and strength is the ability to withstand the stress. When stress becomes greater than strength, accidents happen.
2. For a constant force, a rope breaks due to stress. Which of the following is useful to reduce the stress?
a) Increase the length of the rope
b) Apply small force
c) Increase the cross sectional area of the rope
d) Use a different material of rope
Answer
Answer: c [Reason:] Stress = Force/Area
For a constant force, if the area is small, stress is large. If the area is large, stress is small. Therefore by increasing the cross sectional area stress can be reduced considerably.
3. When a rope is pulled on either side, what is the stress acting on it?
a) Compressive stress
b) Tensile stress
c) Normal stress
d) Tangential stress
Answer
Answer: b [Reason:] A tensile stress occurs when something is being pulled. A rope experiences tensile stress because it is flexible. In other words, a rope cannot be pushed.
4. Fluids cannot resist sheer stress. True or false?
a) True
b) False
Answer
Answer: a [Reason:] Fluids cannot resist sheer stress because they do not deform. Rather they flow. Fluids are opaque to transverse waves therefore they have the inability to undergo sheering stress.
5. What happens when the stress applied to the body is increased beyond the maximum value and is removed after some time?
a) The body will come back to its original position
b) The body will oppose the stress
c) The body becomes hot
d) The body cannot return to its original position
Answer
Answer: d [Reason:] When the applied stress exceeds the maximum value the body does not regain its original position completely after removing external forces. It is said to have reached it elastic limit.
6. A pendulum A oscillating continuously comes to rest after sometime. Now make both pendulums A and B to oscillate simultaneously. What will happen?
a) A comes to rest earlier than B
b) B comes to rest earlier than A
c) A and B comes to rest simultaneously
d) A and B oscillate forever
Answer
Answer: a [Reason:] If a body is subjected to stress or strain continuously, if becomes weak due to elastic fatigue. Therefore A comes to rest earlier than B.
7. What will happen to the elastic property of Gold when Potassium is added to gold?
a) The elastic property of gold decreases
b) The elastic property of gold remains unaltered
c) The elastic property of gold increases
d) Gold loses its elastic property
Answer
Answer: c [Reason:] The addition of impurities causes variation in the elastic property of materials. Potassium when added to gold increases its elasticity thereby making it easy to be electroplated.
8. A copper wire of length 3m and 1mm diameter is subjected to a tension of 5N. Calculate the elongation produced, if the young’s modulus of copper is 120GPa
a) 15m
b) 1800m
c) 0.125 ×10-3 m
d) 15.9mm
Answer
Answer: d [Reason:] Young’s modulus = (Force ×Length)/(Area ×Elongation); Area=πr2
Elongation = (Force ×Length)/(Area ×Young’s modulus)
Elongation = 15.9mm
9. The modulus of rigidity and Poisson’s ratio of the wire are 2.87 × 1010 N/m2 and 0.379 respectively. What is the value of young’s modulus of the material of the wire.
a) 1.08773 × 1010 N/m2
b) 7.915 × 1010 N/m2
c) 7.5725 × 1010 N/m2
d) 0.1403 × 1010 N/m2
Answer
Answer: b [Reason:] Poisson’s ratio = Y/2n – 1
Y=2n(1+Poisson’s ratio)
Y=7.915 × 1010 N/m2
10. What is the effect of hammering on elasticity of materials?
a) Has no effect on elasticity
b) Decreases the elasticity
c) Increases the elasticity
d) Breaks the material
Answer
Answer: c [Reason:] While being hammered or rolled, crystals break into smaller units resulting in increase of their elastic properties.
11. Calculate the Young’s modulus in the cantilever depression method. The length is 1m which is suspended with a load of 150gm. The depression is found to be 4cm. The thickness of the beam is 5mm and breadth is 3cm.
a) 3.92 × 1010 N/m2
b) 9000 × 1010 N/m2
c) 4000 × 1010 N/m2
d) 1.245 ×1010 N/m2
Answer
Answer: a [Reason:] Y = (4gl3)/(bd2 ) × M/y
Y = 3.92 × 1010 N/m2
12. What is the effect of annealing on elasticity of materials?
a) Increases the elasticity
b) Decreases the elasticity
c) Has no effect on elasticity
d) Distorts the material
Answer
Answer: b [Reason:] Annealing is the process of heating a material and then gradually cooling it. While annealing, constituent crystals are uniformly oriented and form larger crystal grains, which results in decrease in their elastic properties.
13. A thick wire is suspended from a rigid support and no load is attached to its free end but the wire is under stress. True or false?
a) True
b) False
Answer
Answer: a [Reason:] The wire is maybe suspended with no load but the wire will experience some stress due to its own weight. Therefore the answer is true.
14. Which type of elasticity is involved in tangential push on the upper face of a block?
a) Bulk modulus
b) Young’s modulus
c) Rigidity modulus
d) Elastic limit
Answer
Answer: c [Reason:] Rigidity modulus is defined as the ration between tangential stress and shearing strain. When a tangential stress is applied to the upper face of a block, the cube gets deformed and there is relative displacement.
15. Air is more elastic than water. True or false?
a) True
b) False
Answer
Answer: False [Reason:] Air can be compressed easily while water is incompressible and bulk modulus is reciprocal of compressibility. Therefore, water is more elastic than air.
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