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## Machine Design MCQ Set 1

1. What results due to addition of surfactants?
a) Ease of diffusion
b) Interfacial mass transfer resistance
c) Ease of mass transfer
d) A cloud over the liquid interface

Answer: b [Reason:] The surfactants which reduce the surface tension results in Interfacial mass transfer resistance.

2. Which of the following is true about rate of mass transfer in gas?
a) NA = kp(pab-pai)
b) NA = kp(cab-cai)
c) NA = kc(pab-pai)
d) NA = kc(cab-cai)

Answer: a [Reason:] For diffusion in gas, partial pressure of the gas is considered.

3. Which of the following is true about rate of mass transfer in liquid?
a) NA = kp(pab-pai)
b) NA = kp(cab-cai)
c) NA = kc(pab-pai)
d) NA = kc(cab-cai)

Answer: d [Reason:] For mass transfer in liquid, molar concentration is considered.

4. Which of the following is the incorrect form of Henry’s law?
a) pA=HAxA
b) pA = cA/HA
c) Xa=HAxA
d) YA = HAxA

Answer: c [Reason:] All are the correct forms of henry’s law except Xa=HAxA.

5. Which of the following is true about overall mass transfer coefficient KL?
a) KL =HA/kp +1/kc
b) 1/KL = HA/kp +1/kc
c) KL =1/HA kp +1/kc
d) 1/KL = HA/kp +kc

Answer: b [Reason:] Using henry’s law and slope point form in the graph we get 1/KL = HA/kp +1/kc.

6. What is the correct expression for overall mass transfer coesfficient based on mole fraction driving forces?
a) 1/Kx = 1/KAky + 1/kx
b) Kx = 1/KAky + 1/kx
c) 1/Kx = KA/ky + 1/kx
d) 1/Kx = 1/KAkx + 1/ky

Answer: a [Reason:] 1/Kx = 1/KAky + 1/kx is the correct representation of overall mass transfer coefficient.

7. What will be the overall mass transfer coefficient when the resistance by gas phase is negligible?
a) 1/Kx = 1/KAky + 1/kx
b) Kx = 1/KAky + 1/kx
c) 1/Kx = KA/ky + 1/kx
d) 1/Kx = 1/KAkx + 1/ky

Answer: b [Reason:] When the resistance by gas is negligible 1/KAky>>1/kx.

8. What are the correct SI units for kx, ky?
a) kmol/s-m
b) kmol/s-m2
c) mol/s-m2
d) kmol/s

Answer: b [Reason:] The SI units for kx and ky is kmol/s-m2.

9. Which of the following is true for mass transfer across liquid-liquid interface?
a) 1/Kx(2) = 1/KAkx(1) + 1/ky(2)
b) 1/Kx(2) = 1/KAky(2) + 1/kx(2)
c) 1/Kx(2) = 1/KAkx(1) + 1/kx(2)
d) 1/Kx(2) = 1/ky(1) + 1/kx(2)

Answer: c [Reason:] For mass transfer across liquid-liquid interface 1/Kx(2) = 1/KAkx(1) + 1/kx(2) holds true.

10. What is the SI unit of kp?
a) kmol/s-m2-pa
b) kmol/s-m-kpa
c) kmol/m2-kpa
d) kmol/s-m2-kpa

Answer: d [Reason:] The value of kp involes partial pressure and its SI unit is kmol/s-m2-kpa.

## Machine Design MCQ Set 2

1. The molar diffusion flux for a cylinder with inner radius r1 and outer radius r2 is directly proportional to:
a) Ln(r2/r1)
b) R2/r1
c) 1/ln(r1/r2)
d) 1/ln(r2/r1)

Answer: d [Reason:] The molar diffusion flux for a cylinder with inner radius r1 and outer radius r2 is 2LDab(ca1-ca2)/ ln(r2/r1).

2. The molar diffusion flux for a plane wall with thickness z2-z1 is directly proportional to:
a) Z2
b) Z2-z1
c) 1/z2-z1
d) Z1-z2

Answer: c [Reason:] The molar diffusion flux for a plane wall with thickness z2-z1 is Dab(ca1-ca2)/ z2-z1.

3. The molar diffusion flux for a spherical shell with inner radius r1 and outer radius r2 is directly proportional to
a) 4r1r2/r2-r1
b) r2-r1/4r1r2
c) r1r2/r2-r1
d) 2r1r2/r2-r1

Answer: a [Reason:] The molar diffusion flux for a spherical shell with inner radius r1 and outer radius r2 is 4r1r2 Dab(ca1-ca2)/r2-r1.

4. For which mass transfer the area log mean is considered?
a) Through a sphere
b) Through a cylinder
c) Through a wall
d) Through a ball

Answer: b [Reason:] The mass transfer through a cylinder is given by the formula 2Lab(ca1-ca2)/ ln(r2/r1).Hence log mean of the area is considered.

5. For which mass transfer the area geometric mean is considered?
a) Through a sphere
b) Through a cylinder
c) Through a wall
d) Through a pipe

Answer: a [Reason:] The molar diffusion flux for a spherical shell with inner radius r1 and outer radius r2 is 4r1r2 Dab(ca1-ca2)/r2-r1.Hence the geometric mean area is considered.

6. The molar diffusion rate of A in stationary B in only z direction is given by:
a) DabA(ΔCa/Δz)
b) DabA(Δz)
c) -DabA(ΔCa/Δz)
d) DabA(ΔCa)

Answer: c [Reason:] The molar diffusion rate of A in stationary B in only z direction is given by -DabA(ΔCa/Δz).

7. For one dimensional diffusion in the radial direction only for cylinder and sphere, the fick’s second law becomes:
a) ΔCa/ΔT= Dab/r(Δ/Δr(rΔCa/Δr)
b) ΔCa/ΔT= Dab/(Δ/Δr(ΔCa/Δr)
c) -ΔCa/ΔT= Dab/r(Δ/Δr(rΔCa/Δr)
d) ΔCa/ΔT= Dab/r(Δ/Δr(r/Δr)

Answer: a [Reason:] For one dimensional diffusion in the radial direction only for cylinder and sphere, the fick’s law becomes ΔCa/ΔT= Dab/r(Δ/Δr(rΔCa/Δr).

8. The fick’s second law is analogous to:
a) Newton;s second law
b) Newton’s third law
c) Fourier’s second law
d) Fourier’s first law

Answer: c [Reason:] The fick’s second law is analogous to fourier’s second law where ca is replaced by temperature T and and Dab by thermal diffusivity.

9. Which equation is concerned with adsorption equilibria.
a) Gibb’s equation
b) Fourier’s law
c) Fick’s law
d) Freundlich’s equation

Answer: d [Reason:] the freunlich’s equation of x/m = Kp1/n is concerned with adsorption equilibria.

10. For a wetted watch tower, what is the area of mass transfer?
a) Rectangular
b) Spherical
c) Cylindrical
d) Hexagonal

Answer: c [Reason:] The shape of a watch tower is cylindrical, hence the area must be cylindrical.

## Machine Design MCQ Set 3

1. The equation of motion for the liquid film in fully developed laminar flow in y-direction is:
a) µd2uy/dx2 + ρg =0
b) µd2uy/dy2 + ρg =0
c) µd2uy/dz2 + ρg =0
d) µd2uy/dx2 = 0

Answer: c [Reason:] Flow is in y direction but changes with respect to z-direction. Hence the equation of motion is µd2uy/dz2 + ρg =0.

2. Which two forces is the reynold’s number a ratio of?
a) Gravitational force and interfacial force
b) Interfacial force and viscous force
c) Thermal conductivity and electrical conductivity
d) Conduction and convection

Answer: b [Reason:] The reynold’s number Nre = 4τ/µ is the ratio of interfacial and viscous force.

3. What value of Reynold’s number is obtained with water?
a) 8
b) 16
c) 25
d) 50

Answer: c [Reason:] The value of 25 is obtained with water.

4. What value of reynold’s number represents a laminar flow?
a) 3
b) 2500
c) 5000
d) 78

Answer: d [Reason:] Only the value of 78 lies between 8 and 1200. SO it represents a laminar flow.

5. Which of the following is correct about Reynold’s number?
a) 3less thanNreless than1200
b) 3less thanreless than1600
c) 25less thanreless than1200
d) 8less thanreless than1200

Answer: d [Reason:] 8less thanreless than1200 are the correct boundary conditions for Reynold’s number.

6. Prandtl’s number is the ratio of which two quantities?
a) Momentum conductivity and thermal conductivity
b) Coefficient of convection to thermal conductivity
c) Momentum diffusivity and thermal diffusivity
d) Interfacial force and viscous force

Answer: c [Reason:] Prandtl’s number is the ratio of Momentum diffusivity and thermal diffusivity.

7. Which of the following is true about prandtl’s number?
a) Npr = Cpµ/k
b) Npr = Cpk/µ
c) Npr = Cvµ/k
d) Npr = Cpµ

Answer: a [Reason:] Prandtl’s number is the ratio of Momentum diffusivity and thermal diffusivity. Hence the formula is Npr = Cpµ/k.

8. What is the physical significance of nusselt’s number?
a) Ratio of convective heat transfer to conductive heat transfer
b) Ratio of convective heat transfer to conductive heat transfer
c) Ratio of total heat transfer to conductive heat transfer
d) Ratio of total transfer to convective heat transfer

Answer: c [Reason:] Nusselt number is the Ratio of convective heat transfer to conductive heat transfer.

9. What is the correct formula for nusselt’s number?
a) hµ/k
b) hρ/k
c) hL/k
d) hΔTL/k

Answer: c [Reason:] The nusselt number hL/k is the ratio of total heat transfer to onductive heat transfer.

10. Which of the following is most true?
a) Na = kcA(cai – ca)
b) Na = kcAΔc
c) Na = kcA(cai – ca)mean
d) Na = kcA(cai – ca)log mean

Answer: b [Reason:] Δc is taken as the driving force and is true every time. It’s expression will change depending upon the conditions.

## Machine Design MCQ Set 4

1. Which of the following is true about turbulent flow?
a) Nre greater than 2000
b) Nre greater than 4000
c) Nre greater than 5000
d) Nre greater than 6000

Answer: a [Reason:] The flow becomes turbulent for a reynold’s number above 4000.

2. Which of the following reynold’s number represents a turbulent flow?
a) 500
b) 700
c) 2500
d) 6000

Answer: d [Reason:] The flow becomes turbulent for a reynold’s number above 4000.

3. Which of the following is present in turbulent flow mass transfer?
a) Slow mass transfer
b) Less mass transfer
c) Eddy currents
d) Eddy diffusion

Answer: d [Reason:] Eddy diffusion is created due to the turbulent flow because of which mass transfer is fast.

4. What is the physical significance of drag coefficient?
a) It is drag force divided by projected area and velocity head
b) It is the ratio of pipe wall shear stress and velocity head
c) It is the ratio of inertial forces to viscous force
d) It is the ratio of inertial force to surface tension force

Answer: a [Reason:] The drag coefficient Cd=2FD/Au2ρ is drag force divided by projected area and velocity head.

5. What is the physical significance of weber number?
a) It is drag force divided by projected area and velocity head
b) It is the ratio of pipe wall shear stress and velocity head
c) It is the ratio of inertial forces to viscous force
d) It is the ratio of inertial force to surface tension force

Answer: d [Reason:] The weber number is the ratio of inertial force to surface tension force.

6. What is the physical significance of lewis number?
a) It is the ratio of bulk transfer mass and molecular diffusion
b) It is the ratio of thermal diffusivity to mass diffusivity
c) It is the ratio of conductive mass transfer to molecular diffusion
d) It is the ratio of mass transfer to mass capacity

Answer: b [Reason:] Lewis number is the ratio of thermal diffusivity to mass diffusivity.

7. What is the Sherwood number analogous to?
a) Schmidt number
b) Lewis number
c) Nusselt number
d) Prandtl number

Answer: c [Reason:] The Sherwood number Nsh =KcL/Dab is analogous to nusselt number.

8. Which of the following equations is referred as reynold’s analogy?
a) f/c = kc/ux
b) f/c = kcux
c) f/2 = kcux
d) f/2 = kc/ux

Answer: d [Reason:] The equation f/2 = kc/ux is referred to as reynold’s analogy.

9. For what condition does the equation for reynold’s analogy equals to equation by Chilton-colburn analogy.
a) Npr=Nre=1
b) Npr=Nse=1
c) Npr=Nsc=1
d) Nsc=Nse=1

Answer: c [Reason:] For Npr=Nsc=1 the equation for reynold’s analogy equals to equation by Chilton-colburn analogy.

10. What is the significance of fanning friction factor?
a) It is the ratio of pipe wall shear stress to velocity head
b) It is drag force divided by projected area and velocity head
c) It is the ratio of inertial forces to viscous force
d) It is the ratio of inertial force to surface tension force

Answer: a [Reason:] The fanning friction factor is the ratio of pipe wall shear stress to velocity head.

## Machine Design MCQ Set 5

1. Determine the rpm(n) of the shaft. diameter(d)=25 mm, cutting speed(cs)=50 m/min.
a) 636.9
b) 202.83
c) 10.615
d) none of the mentioned

Answer: a [Reason:] From the formula, cs= (3.14*d*n)/1000. By putting value of d and cs in above formula, we can easily calculate the value of n.

2. Determine the diameter(d) of the shaft in mm. rpm(n)=25 mm/revolution, cutting speed(cs)=100 mm/min.
a) 21.23
b) 405.47
c) 1273.2
d) none of the mentioned

Answer: c [Reason:] From the formula, cs= (3.14*d*n)/1000. Put n=25 and cs=100 in above equation. We can easily get d as 1273.2 mm.

3. Determine the cutting speed(cs) of the shaft mm/min. diameter(d)=25 mm, rpm(n)=50 mm/revolution
a) 3.925
b) 1.25
c) 7.85
d) none of the mentioned

Answer: a [Reason:] From the formula, cs= (3.14*d*n)/1000. By putting all mentioned values in above equation, we can easily get value of cutting speed.

4. If the diameter of the work surface before machining(d1) is 100 mm and diameter of the machined surface(d2) is 50 mm.
Then the depth of the cut is______ mm.
a) 50
b) 25
c) 15
d) none of the mentioned

Answer: b [Reason:] From the formula, depth of cut=(d1-d2)/2. Here 100-50 equal to 50 and by dividing it by 2 we can get value of depth of cut as 25.

5. Find the metal removal rate from the given data (in mm*mm*mm/minute). cutting speed(cs) =50 mm/minute, depth of cut(d)=10mm, feed(f)= o.1 mm/revolution.
a) 50
b) 500
c) 5000
d) none of the mentioned

Answer: a [Reason:] From the formula, metal removal rate=(cs*d*f). Put the value of cs, d, f in the above equation and you can easily get the value of mrr as 50.

6. Find the cutting speed from the given data (in mm/minute). metal removal rate(mrr) =50 mm*mm*mm/minute, depth of cut(d)=1mm, feed(f)= o.1 mm/revolution.
a) 50
b) 500
c) 5000
d) none of the mentioned

Answer: b [Reason:] From the formula, metal removal rate= (cs*d*f). Put all the values in above equation and you can get the value of cutting speed.

7. Find the feed from the given data (in mm/revolution). cutting speed(cs) =50 mm/minute, depth of cut(d)=100mm, metal removal rate(mrr)= 10 mm/revolution.
a) 0.2
b) 0.02
c) 0.002
d) none of the mentioned

Answer: c [Reason:] From the formula, metal removal rate=(cs*d*f). By putting all values in given equation, you can get the value of feed as 0.002 mm/revolution.

8. Number of revolution = 50, rpm = 100. Find out the machining time.
a) 0.5
b) 2
c) 4
d) none of the mentioned

Answer: a [Reason:] Machining time= revolution/rpm. Here revolution is 5o and rpm is 100. 50/100 =0.5 .

9. The larger diameter of shaft is 125 mm and smaller diameter of the shaft is 95 mm. Find the taper. Assume that length of the job and taper is same.
a) 30
b) 15
c) 60
d) none of the mentioned