Multiple choice question for engineering
Set 1
1. At what temperature, the speed of sound in air will becomes double of its value at 27°C?
a) 54°C
b) 627°C
c) 327°C
d) 927°C
Answer
Answer: d [Reason:] As v∝√T
v/2v=√((273+27)/T)
T=1200K=927℃
2. The speed of a wave in a medium is 760m/s. If 3600 waves are passing through a point in the medium in 2 min, then its wavelength is
a) 13.8m
b) 41.5m
c) 25.3m
d) 57.2m
Answer
Answer: c [Reason:] Number of waves crossing a point per second,
γ=3600/(2×60)=30
ʎ=v/γ=760/30=25.3m
3. An underwater sonar source operating at a frequency of 60 kHz directs its beam towards the surface. If velocity of sound in air is 330m/s, wavelength and frequency of the waves in air are
a) 5.5mm, 60 kHz
b) 5.5mm, 30 kHz
c) 5.5mm, 30 kHz
d) 5.5mm,80 kHz
Answer
Answer: a [Reason:] Frequency in air will also be 60 kHz
ʎa=va/γ=330/(60×103)=5.5×10-3 m
=5.5mm
4. A wave of frequency 100Hz travels along a string towards its fixed end. When this wave travels back, after reflection, a node is formed at a distance of 10cm from the fixed end. The speed of the wave (incident and reflected) is
a) 5m/s
b) 20m/s
c) 10m/s
d) 40m/s
Answer
Answer: b [Reason:] Distance between two successive nodes=ʎ/2=10cm
ʎ=20cm
v=γʎ=100×20=2000=20m/s
5. The first overtone of a stretched wire of given length is 320Hz. The first harmonic is
a) 320Hz
b) 160Hz
c) 480Hz
d) 640Hz
Answer
Answer: b [Reason:] First overtone=2γ=320Hz
First harmonics=γ=160Hz
6. For beats to be produced
a) Frequency of sources should be different and amplitude should be same
b) Frequency of sources should be same and amplitude should be different
c) Frequency of sources should be same and amplitude should be different
d) Frequency of sources should be same and amplitude should be same
Answer
Answer: a [Reason:] For beats formation, frequency of sources should be slightly different and amplitude should be same
7. Sources of sound and observer are moving towards each other, the observer will hear
a) High frequency, low wavelength
b) Low frequency, low wavelength
c) High frequency, low wavelength
d) Low frequency, high wavelength
Answer
Answer: c [Reason:] When source and observer approach each other, frequency of sound increases while wavelength decreases.
8. Reverberation time can’t be controlled by
a) Temperature
b) Size of window
c) Volume of room
d) Changing carpet
Answer
Answer: d [Reason:] Reverberation time is the time which sound takes to fall in intensity to one millionth part of its original intensity
9. Pressure variation of mechanical wave depends upon us
a) ∝Intensity
b) Independent of intensity
c) ∝1/Intensity
d) Intensity2
Answer
Answer: c [Reason:] Pressure amplitude vibration in a medium∝Amplitude of the wave (A)
Hence pressure variation is proportional to the intensity of the wave
10. 50 tuning forks are arranged in increasing order of their frequencies such that each gives 4 beats/sec with its previous tuning fork. If the frequency of the last fork is octave of the first, then the frequency of the first tuning fork is
a) 200Hz
b) 204Hz
c) 196Hz
d) 0
Answer
Answer: c [Reason:] 2v=v+49×4
v=196Hz
Set 2
1. Coefficient of kinetic friction is less than the coefficient of static friction. True or false?
a) True
b) False
Answer
Answer: a [Reason:] The value of kinetic energy is direction proportional to the normal reaction between the two surfaces. Thus the coefficient of kinetic friction is less than the coefficient of static friction.
2. The coefficient of static friction is
a) Less than the coefficient of kinetic friction
b) Greater than the coefficient of limiting friction
c) Equal to coefficient of kinetic friction
d) Equal to the tangent of the angle of friction
Answer
Answer: d [Reason:] The angle which the resultant of the limiting friction and the normal reaction which makes the normal reaction is called the angle of friction. But the tangent of the angle of friction is equal to the coefficient of static friction.
3. Which of the following kinetic friction is smaller?
a) Limiting friction
b) Static friction
c) Rolling friction
d) Sliding friction
Answer
Answer: c [Reason:] The force which comes into play when a body rolls over the surface of another body is called rolling friction. For the same magnitude of normal reaction, rolling friction is always greater than the sliding friction.
4. A cubical block rests on an inclined plane of μ = 1/√3, determine the angle of inclination when the block just slides down the inclined plane
a) 40°
b) 50°
c) 30°
d) 20°
Answer
Answer: c [Reason:] When the block just slides down the inclined plane, the angle of inclination is equal to the angle of response.
tan α = μ= 1/√3
α = 30°
5. A mass of 4kg rests on a horizontal plane. The plane is gradually inclined until at an angle θ= 15° with the horizontal, the mass just begins to slide. What is the coefficient of static friction between the block and the surface?
a) 0.814
b) 0.27
c) 1.5
d) 3.5
Answer
Answer: b [Reason:] θ = 15° is the angle of response.
Coefficient of friction, μ = tan θ = tan 15° = 0.27
6. A scooter weighs 120kg f. Brakes are applied so that wheels stop rolling and start skidding. Find the force of friction if the coefficient of friction is 0.4.
a) 60kg f
b) 48kg f
c) 25kg f
d) 32kg f
Answer
Answer: b [Reason:] Weight of the scooter = 120kg f
μ = 0.4
f = μ×weight of the scooter = 0.4×120 = 48kg f
7. How is friction due to air reduced?
a) Streamlining
b) Lubrication
c) By using ball bearings
d) By polishing
Answer
Answer: a [Reason:] Friction due to air is considerably reduced by streamlining the shape pf the body moving through air. For example, jets have streamline shape.
8. Friction can be increased by
a) Using air cushion
b) Lubricants
c) Using sand
d) Using ball bearings
Answer
Answer: c [Reason:] By throwing sand the force of friction between the wheels and the track becomes easier. On rainy days, we throw sand on the slippery ground. This increases the friction between our feet and the ground, and reduces the chance of slipping.
9. When moving along a curved path, he
a) Leans inwards
b) Leans outwards
c) Is still
d) Leans sideways
Answer
Answer: a [Reason:] When a cyclist goes around a curved path, a centripetal force is required. The force between the tyres and the road is small to provide the necessary centripetal force. That is why a cyclist going around a curve leans inwards because the horizontal component of the normal reaction provides the necessary centripetal force.
10. A train has to negotiate a curve of radius 400m. By how much should the putter rail be raised with respect to inner rail for speed of 48 km/h? The distance between the rails is 1m.
a) 0.20m
b) 0.0454m
c) 0.45m
d) 0.020m
Answer
Answer: b [Reason:] h = (v2 l)/rg
h = 402/32 = 0.0454m
Set 3
1. When a body falls freely under gravity, then the work done by the gravity is
a) Positive
b) Negative
c) Zero
d) Infinity
Answer
Answer: a [Reason:] If a force acting on a body has a component in the direction of displacement, then the work done by the force is positive. Hence when a body falls freely under the influence of gravity the work done by the gravity is positive.
2. When a gas filled in a cylinder fitted with a movable piston is allowed to expand, the work done by the gas is positive. True or false?
a) True
b) False
Answer
Answer: a [Reason:] When a gas filled win a cylinder fitted with movable piston is allowed to expand, the work done by the gas is positive, because the force due to gas pressure and displacement act in the same direction.
3. When a body slides against a rough horizontal surface, the work done by friction is
a) Positive
b) Zero
c) Negative
d) Constant
Answer
Answer: c [Reason:] If a force acting on a body has a component in the opposite direction of displacement, the work done is negative, when a body slides against a rough horizontal surface, its displacement is opposite to that of the force of friction. He work done by the friction is negative.
4. When a body is lifted, the work done by the gravitational force is positive. True or false?
a) True
b) False
Answer
Answer: b [Reason:] When a body is lifted, the work done by the gravitational force is negative. This is because the gravitational force acts vertically downwards while the displacement is in vertically upward direction.
5. For a body moving in a circular path, the work done by the centripetal force is
a) Negative
b) Positive
c) Constant
d) Zero
Answer
Answer: d [Reason:] For a body moving in a circular path, the centripetal force and the displacement are perpendicular to each other. So the work done by the centripetal force is zero.
6. When a coolie walks on a horizontal platform with a load on his head, the work done by the coolie on the load is zero. True or false?
a) True
b) False
Answer
Answer: a [Reason:] When a coolie walks on a horizontal platform with load on his head, he applies force in the upward direction equal to its weight. The displacement of the load is along the horizontal direction. Thus the work done by the coolie on the load is zero.
7. A gardener pushes a lawn roller through a distance of 20m. If he applies a force of 20kg weight in a direction inclined at 60° to the ground, find the work done by him. (g=9.8m/s2)
a) 400J
b) 1960J
c) 250J
d) 2514J
Answer
Answer: b [Reason:] F = 20kg wt = 20×9.8N
s = 20m
θ = 60°
W = Fscosθ = 20×9.8×20×cos60°
W = 1960J
8. A person is holding a bucket by applying a force of 10N. He moves a horizontal distance of 5m and then climbs up a vertical distance of 10m. Find the total work done by him
a) 50J
b) 150J
c) 100J
d) 200J
Answer
Answer: c [Reason:] F = 10N, s = 5m, θ = 90°
Work done, W1=Fscosθ = 10×5×cos90° = 0
For vertical motion, the angle between force and displacement is 0°.
Here, F = 10N, s = 10m, θ=0°
Work done, W2=10×10×cos0 = 100J
Total work done = W1+W2 = 100J
9. A moving hammer drives a nail into the wood. It has kinetic energy. True or false?
a) True
b) False
Answer
Answer: a [Reason:] A moving hammer possesses kinetic energy as it is in a virtue of motion. A moving object can do work. Therefore a moving hammer drives a nail into the wood.
10. A bullet fired from a gun can pierce a target due to its
a) Mechanical energy
b) Heat energy
c) Kinetic energy
d) Acceleration
Answer
Answer: c [Reason:] The kinetic energy of a body by virtue of its motion is called kinetic energy. A moving object can do work. Therefore a bullet fired from a gun can pierce a target due to its kinetic energy.
Set 4
1. What is the molecular distribution breadth for polymerization reaction of trifunctional monomers, if the conversion is 90%?
a) 0.344
b) 1.344
c) 0.33
d) none of the mentioned
Answer
Answer: b [Reason:] The distribution breadth for polyfunctional system is expressed as,
Xn/Xw= 1+ fp/(fp+1-p)2
And p=0.9, f=3
Thus, distribution breadth is 1.344.
2. Hydroxyacid is allowed to polymerize in the presence of another trifunctional monomer containing carboxylic groups. What kind of structure is formed at the end of the reaction?
a) linear
b) branched
c) cross-linked
d) none of the mentioned
Answer
Answer: b [Reason:] At the end of the reaction only branched structure is formed and no cross-linked structures can be formed since no bifunctional hydroxyl monomers are present to combine the branches.
3. Which of the following monomer molecule’s presence could lead to the formation of cross linking polymer, when hydroxyl caproic acid and carboxyl acid monomers (f>2) are polymerized together?
a) glycol
b) ethanol
c) diamines
d) none of the mentioned
Answer
Answer: a [Reason:] Glycol is a bifunctional monomer having hydroxyl groups which will establish cross-links by combining two branches.
4. How does weight fraction distribution vary with increasing functionality at constant conversion?
a) gets broader
b) gets narrower
c) remains constant
d) none of the mentioned
Answer
Answer: a [Reason:] The weight fraction distribution broadens with increasing functionality at comparable conversion values.
5. What is true about the branching system involving trifunctional monomers?
a) weight fraction of monomer lower than other species
b) weight fraction of bigger species become higher progressively
c) weight fraction of monomer always larger than other species
d) none of the mentioned
Answer
Answer: c [Reason:] The weight fraction of the monomer is always greater than any of the other species and the weight fraction of larger species being lower, progressively, in such a gelling system involving trifunctional monomers.
6. How does the weight distribution vary with increasing conversion and constant trifunctionality?
a) gets broader
b) gets narrower
c) remains constant
d) none of the mentioned
Answer
Answer: a [Reason:] The distribution broadens as the extent of reaction is increased, keeping the functionality same.
7. At 100% completion of reaction, only gel is present and the distribution breadth, Xw/Xn becomes infinite. State true or false.
a) True
b) False
Answer
Answer: b [Reason:] At p=1, the whole system is converted into an insoluble and infusible mass of one giant molecule and distribution breadth becomes equal to unity.
8. Which is the correct expression for number average degree of polymerization for the non-linear multi-functional systems?
a) 1/{1-(pf/2)}
b) (1+p)/{1-(f-1)p}
c) 1-(pf/2)
d) 1/(pf/2)
Answer
Answer: a [Reason:] The general expression for Xn for non-linear multi-functional system is given by,
Xn= 1/{1-(pf/2)}.
9. Before the interaction of W3 and W4 curves in the given figure, the system consists of most weight abundant species. State true or false.
a) true
b) false
Answer
Answer: b [Reason:] The gel formed comprises of the most weight abundant species, beyond the intersection of the the curves W3 and W4.
10. What is the weight average degree of polymerization for non-linear trifunctional system, if the conversion is 0.3?
a) 2.35
b) 3.25
c) 5.5
d) 1.82
Answer
Answer: b [Reason:] The expression for Xw, for non-linear trifunctional system is given by,
Xw = (1+p)/{1-(f-1)p}
Substituting the values we get, Xw as 3.25.
Set 5
1. What is the correct structure of monomer of poly methyl methacrylate?
a) CH2═C(CH3)−CO−O−CH3
b) CH3−CO−O−CH3
c) CH3−CO−O−CH═CH2
d) CH3−CO−O−C(CH3)═CH2
Answer
Answer: a [Reason:] The structure of methyl methacrylate is given by- CH2═C(CH3)−CO−O−CH3
It is the monomer of the polymer polymethyl methacrylate (PMMA).
2. Which of the following mechanism is used in the formation of commercially used polymethyl methacrylate?
a) anionic mechanism
b) cationic mechanism
c) free radical mechanism
d) cannot be said
Answer
Answer: c [Reason:] Methyl Methacrylate when polymerized by free radical initiated bulk or suspension polymerization, using peroxide or azonitrile initiators at about 100 ᵒC, gives polymethyl methacrylate as the final product.
3. What is the glass transition temperature of the polymer polymethyl methacrylate?
a) 74ᵒ C
b) 105ᵒ C
c) 93ᵒ C
d) 80ᵒ C
Answer
Answer: b [Reason:] PMMA has a glass transition temperature of about 105 ᵒC and a service temperature of about 93 ᵒC. It has heat deflection temperature in the range of 74 to 100 ᵒC.
4. What is the specialized application of PMMA, keeping in mind its excellent optical clarity and high atmospheric resistance?
a) hard contact lenses
b) construction
c) decoration of appliances
d) insulation wires
Answer
Answer: a [Reason:] The combination of excellent optical clarity and outstanding weathering behavior makes PMMA especially useful for hard contact lenses. It is good for the applications that require light transmission and outdoor exposure.
5. For the production of sheets, rods, etc. by bulk polymerization of methylmethacrylate, the complete polymer syrup of high viscosity is poured into the casting cell, just to minimize reaction exotherm and shrinkage. State true or false.
a) true
b) false
Answer
Answer: b [Reason:] For the production of sheets, rods, etc. by bulk polymerization of methylmethacrylate, the monomer methylmethacrylate, firstly is partially polymerized and then the prepolymer syrup of convenient viscosity is poured into the casting cell. This is done to minimize reaction exotherm and obtain sheets free of sink marks and voids.
6. How does the solubility of polyacrylates in oils and hydrocarbons vary with the length of side group attached?
a) increases
b) decreases
c) remains same
d) increases then decreases
Answer
Answer: a [Reason:] The solubitlity of polyacrylates in oils and hydrocarbon increases with the increase in size of the side group attached. The polymer also gets harder and tougher with the decreases in the size of group.
7. Which of the following polyacrylate is used in paints and adhesives formulation?
a) poly (butyl acrylate)
b) poly (methyl acrylate)
c) poly (2-ethylhexyl acrylate)
d) poly (ethyl acrylate)
Answer
Answer: c [Reason:] Poly(2-ethylhexyl acrylate) is having a large size ester group which makes it quite softer and so it is used in painting and adhesion formulation.
8. Which of the following monomer can copolymerize with acrylonitrile to improve the dyeability of the acrylic fibre?
a) vinyl acetate
b) methacrylic acid
c) vinyl pyrrolidone
d) all of the mentioned
Answer
Answer: d [Reason:] To improve dyeability, feel and texture of acrylic fibre, the polymer is prepared by copolymerizing with 5-15% of monomers like vinyl pyrrolidone, vinyl acetate and methacrylic acid with acrylonitrile.
9. Which of the following properties are not true about polyacrylonitrile?
a) monomer solubility
b) yellowing on heating
c) soluble in dimethyl formamide
d) suffers discoloration on heating
Answer
Answer: a [Reason:] Acrylonitrile is a non-solvent for its own polymer and hence, it undergoes heterogeneous polymerization using redox catalyst. On heating, it easily suffers discoloration and starts yellowing and the later turns black. It is soluble in solvents like dimethyl formamide, dimethyl sulphoxide, etc.
10. How is the polymer formed by polymerization of acrylonitrile obtained in the form of?
a) homogeneous solution
b) suspension
c) precipitate
d) colloids
Answer
Answer: c [Reason:] Acrylonitrile undergoes heterogeneous aqueous polymerization in the presence of redox catalyst and the polymer is obtained in the form of precipitate.
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