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Multiple choice question for engineering

Set 1

1. Fractional distillation is a process of separation of
a) 2 miscible liquids
b) 2 immiscible liquids
c) 1 miscible and 1 immiscible liquids
d) None of the mentioned

View Answer

Answer: a [Reason:] Fractional distillation is a process of separation of 2 immiscible liquids. Fractional distillation is the separation of a mixture into its component parts, or fractions, separating chemical compounds by their boiling point by heating them to a temperature at which one or more fractions of the compound will vaporize.

2. Difference in boiling point of 2 liquid in fractional distillation is
a) Greater than 25 K
b) Less than 25 K
c) Equal to 25 K
d) None of the above options

View Answer

Answer: b [Reason:] Difference in boiling point of 2 liquid in fractional distillation is is less than 25 K. Fractional distillation is the separation of a mixture into its component parts, or fractions, separating chemical compounds by their boiling point by heating them to a temperature at which one or more fractions of the compound will vaporize.

3. A simple fractional tube is packed with
a) Wooden beads
b) Plastic beads
c) Metal beads
d) Glass beads

View Answer

Answer: d [Reason:] A simple fractional tube is packed with glass beads. The fractional distillation column is set up with the heat source at the bottom on the still pot.

4. Fractional distillation is different from distillation because of the presence of
a) Fractionating column
b) Condenser
c) Distillation flask
d) Conical flask

View Answer

Answer: a [Reason:] Fractional distillation is different from distillation because of the presence of fractionating column. A laboratory fractionating column is a piece of glassware used to separate vaporized mixtures of liquid compounds with close volatility.

5. The beads are provided in fractional column for
a) Vapours to generate
b) Vapours to condense
c) Vapours to evaporate
d) All of the mentioned

View Answer

Answer: b [Reason:] The beads are provided in fractional column for vapours to condense. The fractional distillation column is set up with the heat source at the bottom on the still pot.

6. Select the incorrect statement from the following options.
a) Fractionating columns are available in various design and size
b) Fractionating columns are available according to one fixed standard
c) A simple fractionating column is a tube packed with glass beads
d) Fractional distillation is the process of separation of different gases from air

View Answer

Answer: b [Reason:] Fractionating columns are available in various design and size and not according to one fixed standard.

7. Which of the following gases cannot be separated from air using fractional distillation?
a) Argon
b) Oxygen
c) Helium
d) Nitrogen

View Answer

Answer: c [Reason:] Helium gas cannot be separated from air using fractional distillation. Fractional distillation is used in air separation, producing liquid oxygen, liquid nitrogen, and highly concentrated argon.

8. Initially, the temperature at the top of the column is _______________ than at its bottom.
a) Greater
b) Lesser
c) Equal
d) None of the mentioned

View Answer

Answer: b [Reason:] The temperature at the top of the column is lesser than at its bottom. The two major types of distillation columns used are tray and packing columns.

9. Which of the following is more suitable for fractional distillation process?
a) Oil bath
b) Water bath
c) Glycerine bath
d) None of the mentioned

View Answer

Answer: a [Reason:] Oil bath is the most suitable option for the fractional distillation process. Vacuum distillation systems operate at reduced pressure, thereby lowering the boiling points of the materials. Anti-bumping granules, however, become ineffective at reduced pressures.

10. Number of steps required for the separation of two liquids in fractional distillation is
a) 1
b) 2
c) 3
d) 4

View Answer

Answer: b [Reason:] Number of steps required for the separation of two liquids in fractional distillation is 2. Vacuum distillation systems operate at reduced pressure, thereby lowering the boiling points of the materials. Anti-bumping granules, however, become ineffective at reduced pressures.

Set 2

1. Which of the following is not an application of nylon-6, 6?
a) Durable hair combs
b) Adhesives
c) Tyre cords
d) Medicine and pharmacy

View Answer

Answer: b [Reason:] Durable hair combs, tyre cords, medicine and pharmacy are some of the applications of nylon-6, 6.

2. Nylon-6, 6 have application in medicine and pharmacy because of
a) Elasticity
b) Toughness
c) Good hydrocarbon resistance
d) Sterilisability

View Answer

Answer: d [Reason:] Nylon-6, 6 have application in medicine and pharmacy because of sterilisability. It is also used as an engineering material in bearings and gears due to its good abrasion resistance and self-lubricating properties.

3. The other name for dacron is
a) Polyethylene terephthalate
b) Polyacrylonitrile
c) Polyamidenitrile
d) Polyethylene caprolactum

View Answer

Answer: a [Reason:] The other name for dacron is polyethylene terephthalate. It is the most common thermoplastic polymer resin of the polyester family and is used in fibers for clothing, containers for liquids and foods.

4. PET is prepared by heating dimethyl terephthalate and ethylene glycol in
a) Acidic medium
b) Basic medium
c) Neutral medium
d) Water

View Answer

Answer: b [Reason:] PET is prepared by heating dimethyl terephthalate and ethylene glycol in basic medium at moderate pressure (2.7–5.5 bar) and high temperature (220–260 °C).

5. Terephthalic acid is converted into its dimethyl ester by treating it with
a) Methyl chloride
b) Hydroxylamine
c) Methyl alcohol
d) Ethylene glycol

View Answer

Answer: c [Reason:] Terephthalic acid is converted into its dimethyl ester by treating it with methyl alcohol. At high temperature, TPA crystals constantly dissolve and reform which increases release of 4-formylbenzoic acid in solution where oxidation can be completed.

6. State true or false. Blends of terylene fibers with wool have better crease and wrinkle resistance, they are more durable, higher strength, do not shrink and are not attacked by moths.
a) True
b) False

View Answer

Answer: a [Reason:] Blends of terylene fibers with wool have better crease and wrinkle resistance, they are more durable, higher strength, do not shrink and are not attacked by moths. Terylene polyester staple fiber is being used in staple-fibre form in blends with both natural and other synthetic fibers.

7. Which of the following is not an application of dacron?
a) Magnetic recording tapes
b) Wide-necked jars for coffee
c) Car heater
d) Window shades

View Answer

Answer: d [Reason:] Magnetic recording tapes, wide-necked jars for coffee, car heater are some of the applications of dacron.

8. Acrylonitrile is
a) Vinyl chloride
b) Methyl alcohol
c) Methyl chloride
d) Vinyl cyanide

View Answer

Answer: d [Reason:] Acrylonitrile is vinyl cyanide. It is an organic compound with the formula CH2CHCN and is colorless volatile liquid, although commercial samples can be yellow due to impurities.

9. Select the incorrect statement from the following option.
a) Orlon is the trade name of polyacrylonitrile
b) Orlon fibers are quick drying and resistant to water
c) Orlon fibers are less resistant to acid, gases than nylon
d) Orlon fibers are used for manufacturing window shades

View Answer

Answer: c [Reason:] Orlon fibers are more resistant to acid, gases than nylon. All the other options are correct.

10. State true or false. Polyacrylonitrile can be dissolved in its monomer so it can be shaped by bulk casting.
a) True
b) False

View Answer

Answer: b [Reason:] Polyacrylonitrile does not dissolved in its monomer so it cannot be shaped by bulk casting.

Set 3

1. A cylinder rolls up an inclined plane, reaches some height and then rolls down (without slipping throughout these motions). The direction of the frictionless force acting on the cylinders is
a) Up the incline, while ascending and down the incline, while descending
b) Up the incline, while ascending as well as descending
c) Down the incline, while ascending and up the incline, while descending
d) Down the incline, while ascending as well as descending

View Answer

Answer: b [Reason:] Whether the cylinder rolled up or down, the centre of mass and hence the point of contact of the cylinder has an acceleration g sinθ in the downward direction. Hence in both cases, the force of friction acts up the inclined plane.

2. A solid sphere is rotating in free space. If the radius of the sphere is increased keeping mass same, which one of the following will not be affected?
a) Moment of inertia
b) Angular momentum
c) Angular velocity
d) Rotational kinetic energy

View Answer

Answer: b [Reason:] As the radius increases, the moment of inertia of the sphere increases. As no external torque acts in free space, the speed of rotation decreases but the angular momentum remains constant.

3. A thin circular ring of mass m and radius R is rotating about its axis with a constant angular velocityω. Two objects each of mass M are attached gently to the opposite ends of a diameter of the ring. The ring now rotates with an angular velocity ω, which is equal to
a) mω/(m+M)
b) mω/(m+2M)
c) ((m+2m)ω)/m
d) ((m-2M)ω)/((m+2M))

View Answer

Answer: b [Reason:] By conservation of angular momentum, (m+2M)R2 ω=mR2 ω ω=mω/(m+2M)

4. A solid sphere, a hollow sphere and a ring are released from top of an inclined plane (frictionless) so that they slide down the plane. Then, maximum acceleration down the plane is for (No rolling)
a) Solid sphere
b) Hollow sphere
c) Ring
d) All same

View Answer

Answer: d [Reason:] As the bodies slide and do not roll, they all have the same acceleration, a=gsinθ

5. In a bicycle the radius of rear wheel is twice the radius of the front wheel. If rf and rr are the radii vf and vr are the speeds of top most points of wheels, then
a) vr=2vf
b) vf=2vr
c) vr=vf
d) vr is lesser than vf

View Answer

Answer: c [Reason:] Speeds of the top most points of both wheels will be equal and equal to that of centre of mass of the car.

6. Two rings of radii R and nR made from the same wire have the ratio of moments of inertia about an axis passing through their centre equal to 1:8. The value of n is
a) 2
b) 2√2
c) 4
d) ½

View Answer

Answer: a [Reason:] As radius of second ring is n times, length and hence mass of wire used is also n times. I1/I2 =(MR2)/(nM(nR)2)=1/n3 =1/8 Therefore, n=2

7. In an orbital motion, the angular momentum vector is
a) Along the radius vector
b) Parallel to the linear momentum
c) In the orbital plane
d) Perpendicular to the orbital plane

View Answer

Answer: d [Reason:] In an orbital motion, the direction of angular momentum vector is perpendicular to the orbital plane.

8. If there is change of angular momentum from J to 4J in 4s, then the torque is
a) (3/4) J
b) 1J
c) (5/4) J
d) (4/3) J

View Answer

Answer: a [Reason:] τ=dL/dt τ=(4J-J)/4=3/4 J

9. A horizontal platform is rotating with uniform angular velocity ω around the vertical axis passing through its centre. At some instant of time, a viscous liquid of mass m is dropped at the centre and is allowed to spread pout and finally fall. The angular velocity during this period
a) Decreases continuously
b) Decreases initially and increases again
c) Remains unaltered
d) Increases continuously

View Answer

Answer: b [Reason:] By conservation of angular momentum, L = Iω=constant As the liquid is dropped, it starts spreading out. The moment of inertia increases and angular velocity decreases. As the liquid starts falling, the moment of inertia again decreases and the angular velocity increase.

Set 4

1. There is some water in a breaker 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

View Answer

Answer: b [Reason:] 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 direction of his motion. True or false?
a) True
b) False

View Answer

Answer: b [Reason:] 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. True or false?
a) True
b) False

View Answer

Answer: a [Reason:] 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

View Answer

Answer: d [Reason:] 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

View Answer

Answer: c [Reason:] For its revolution in 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 same velocity. True or false?
a) True
b) False

View Answer

Answer: a [Reason:] 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

View Answer

Answer: d [Reason:] 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 net force acting a kite skilfully held stationary in air?
a) Zero
b) Infinity
c) Constant
d) Cannot be predicted

View Answer

Answer: a [Reason:] As the kite is held stationary, the net force acting on it is zero. The force exerted by 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

View Answer

Answer: c [Reason:] 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

Set 5

1. What will be the length of mercury column in a barometer tube, when the atmospheric pressure is 75cm of mercury and the tube is inclined at an angle of 60° with the horizontal direction?
a) 8.66cm
b) 86.6cm
c) 866cm
d) 0.866cm

View Answer

Answer: b [Reason:] If l is the length of mercury column in the barometer tube, then h/l=sin60 75/l=√3/2 l=(75×2)/√3=86.6cm

2. The density of the atmosphere at sea level is 1.29kgm-3. Assume that is does not change with altitude. Then how high would the atmosphere extend? (g=9.8mm-2)
a) 0.5km
b) 0.8km
c) 8km
d) 80km

View Answer

Answer: c [Reason:] Pa=hρg h=Pa/ρg=(1.01×105)/(1.29×9.81)=7981m=8km(approx)

3. It is painful to walk barefooted on the ground covered with edged pebbles. True or false?
a) True
b) False

View Answer

Answer: a [Reason:] While walking, when entire weight of our body gets supported on the sharp edge of any pebble, it will exert a large pressure on our feet due to reaction. This causes considerable pain on our feet.

4. A closed compartment containing gas in moving with some acceleration on horizontal direction. Neglect effect of gravity. Then the pressure in the compartment is
a) Same everywhere
b) Lower in the front side
c) Lower in the rear side
d) Lower in the upper side

View Answer

Answer: b [Reason:] As the compartment has acceleration in the forward direction, the gas molecules experience an acceleration in the backward direction. This lowers the pressure in the compartment in the front side.

5. Statement 1: The stream of water flowing at high speed from a garden hose pipe tends to spread like a fountain when held vertically up, but tends to narrow down when held vertically down.
Statement 2: In any steady flow of an incompressible fluid, the volume flow rate of the fluid remains constant.
a) Statement 1 is true, statement 2 is true. Statement 2 is a correct explanation for statement 1
b) Statement 1 is true, statement 2 is true. Statement 2 is not a correct explanation for statement 1
c) Statement 1 is true, statement 2 is false
d) Statement 1 is false, statement 2 is true

View Answer

Answer: a [Reason:] Volume rate of flow, Q=Av = constant As speed of upstream decreases, its area of cross-section increases. As speed of downstream increases, its area of cross-section decreases.

6. If two soap bubbles of different radii are connected by a tube,
a) Air flow from the bigger bubble to the smaller bubble till the sizes become equal
b) Air flows from bigger bubble to the smaller bubble till the sizes are interchanged
c) Air flows from the smaller bubble to the bigger
d) There is no flow of air

View Answer

Answer: c [Reason:] The excess pressure inside of a soap bubble is inversely proportional to its radius. So, the pressure is more inside the smaller bubble than the bigger bubble. When these two bubbles are connected by a tube, air will flow from the smaller bubble to the bigger bubble.

7. A 20cm long capillary tube is dipped in water. The water rises up to 8cm. If the entire arrangement is put in a freely falling elevator the length of water column in the capillary tube will be
a) 4cm
b) 20cm
c) 8cm
d) 10cm

View Answer

Answer: b [Reason:] In the freely falling elevator, the entire arrangement is in a state of weightlessness, g = 0. So, water will rise (h = 2σcosθ/rρg ) to fill the entire 20cm length of the tube.

8. Assertion: A this stainless steel needle can lay floating on a still water surface [Reason:] Any objection floats, when the buoyancy force balances the weight of the object
a) Both assertion and reason are true and reason is the correct explanation of the assertion
b) Both assertion and reason are true but reason is not the correct explanation of the assertion
c) Assertion is true but reason is false
d) Assertion and reason is false

View Answer

Answer: c [Reason:] The assertion is true but the reason is false. The needle floats when the upward tension on the needle balances its weight.

9. At critical temperature, the surface tension of a liquid
a) Is zero
b) Is infinity
c) Is the same as any other temperature
d) Cannot be determined

View Answer

Answer: a [Reason:] At critical temperature, the surface tension of a liquid becomes zero.

10. In a capillary tube experiment, a vertical, 30 cm long capillary tube is dipped in water. The water rises up to a height of 10 cm due to capillary action. If this experiment is conducted in a freely falling elevator, the length of the water column becomes
a) 10 cm
b) 20 cm
c) 30 cm
d) Zero

View Answer

Answer: c [Reason:] In the freely falling elevator, g = 0. Water will rise (h=2σcosθ/rρg) to fill the entire 30 cm length of the tube.