McqMate
These multiple-choice questions (MCQs) are designed to enhance your knowledge and understanding in the following areas: Mechanical Engineering .
| 1. |
The specific gravity of a liquid has |
| A. | the same unit as that of mass density |
| B. | the same unit as that of weight density |
| C. | the same unit as that of specific volume |
| D. | no unit |
| Answer» D. no unit | |
| Explanation: the specific gravity of a liquid is the ratio of two similar quantities (densities) which makes it unitless. | |
| 2. |
The specific volume of a liquid is the reciprocal of |
| A. | weight density |
| B. | mass density |
| C. | specific weight |
| D. | specific volume |
| Answer» B. mass density | |
| Explanation: specific volume(v) is defined as the volume(v ) per unit mass(m). | |
| 3. |
Which one of the following is the unit of specific weight? |
| A. | n = m3 |
| B. | n = m2 |
| C. | n = m |
| D. | n = ms |
| Answer» A. n = m3 | |
| Explanation: specific weight(γ) is defined as the weight(w) per unit volume(v ), i.e., | |
| 4. |
[p] = [m]/[v] = [m] /[L3] = [ML-3]. |
| A. | [m1 l-3 t0]. |
| B. | [m1 l0 t0]. |
| C. | [m0 l-3 t0]. |
| D. | [m0 l0 t0]. |
| Answer» D. [m0 l0 t0]. | |
| Explanation: the specific gravity of a liquid is the ratio of two similar quantities (densities) which makes it dimensionless. | |
| 5. |
Which one of the following is the |
| A. | [m1 l-3 t0]. |
| B. | [m-1 l3 t0]. |
| C. | [m-1 l-3 t0]. |
| D. | [m0 l3 t0]. |
| Answer» B. [m-1 l3 t0]. | |
| Explanation: specific volume(v) is defined as the volume(v ) per unit mass(m). thus, [v] = [v]/[m] = [l3]/[m] = [m-1l3]. | |
| 6. |
the relation between their specific volumes v1 and v2? |
| A. | v1 > v2 |
| B. | v1 < v2 |
| C. | v1 = v2 |
| D. | cannot be determined due to insufficient information. |
| Answer» B. v1 < v2 | |
| Explanation: specific volume(v) is defined as the volume(v ) per unit mass(m). | |
| 7. |
mark of one litre and weighed. The weight of the liquid is found to be 6.5 N. The specific weight of the liquid will be |
| A. | 6:5 kn = m3 |
| B. | 6:6 kn = m3 |
| C. | 6:7 kn = m3 |
| D. | 6:8 kn = m3 |
| Answer» A. 6:5 kn = m3 | |
| Explanation: specific weight(γ) is defined as the weight(w) per unit volume(v ), i.e., | |
| 8. |
A beaker is filled with a liquid up to the mark of one litre and weighed. The weight of the liquid is found to be 6.5 N. The specific gravity of the liquid will be |
| A. | 0.65 |
| B. | 0.66 |
| C. | 0.67 |
| D. | 0.68 |
| Answer» A. 0.65 | |
| Explanation: specific gravity(s) of a liquid is defined as the ratio of the density of the liquid(pl) to that of water(pw). | |
| 9. |
mark of one litre and weighed. The weight of the liquid is found to be 6.5 N. The specific volume of the liquid will be |
| A. | 1 l =kg |
| B. | 1:5 l =kg |
| C. | 2 l =kg |
| D. | 2:5 l =kg |
| Answer» B. 1:5 l =kg | |
| Explanation: specific volume(v) is defined as the volume(v ) per unit mass(m). thus, | |
| 10. |
continuity equation is |
| A. | mass conservation |
| B. | zeroth law of thermodynamics |
| C. | first law of thermodynamics |
| D. | energy conservation |
| Answer» A. mass conservation | |
| Explanation: continuity equation is derived from the mass conservation principle. it states that for an isolated system, the mass of the system must remain constant. | |
| 11. |
equation of mass conservation into the conservative integral form, which of these theorems is used? |
| A. | stokes theorem |
| B. | kelvin-stokes theorem |
| C. | gauss-siedel theorem |
| D. | gauss divergence theorem |
| Answer» D. gauss divergence theorem | |
| Explanation: the expansion of non- conservative integral equation gives two volume integral terms. one of these terms representing the mass flow is converted into surface integral using the gauss divergence theorem. | |
| 12. |
ρV→. dS→ is positive when |
| A. | the mass flow is outward |
| B. | the mass flow is inward |
| C. | the mass flow is positive |
| D. | the mass flow is negative |
| Answer» A. the mass flow is outward | |
| Explanation: ds→ always points outwards to the control volume. so, the product ρv→. ds→ is positive when the mass flow is outwards. | |
| 13. |
Hydraulic gradient line takes into consideration |
| A. | potential and kinetic heads only |
| B. | potential and pressure heads only |
| C. | kinetic and pressure heads only |
| D. | potential, kinetic and pressure heads |
| Answer» B. potential and pressure heads only | |
| Explanation: hgl is obtained by plotting piezometric head at various points along the axis of the pipe. | |
| 14. |
Which of the following is true? |
| A. | egl always drops in the direction of c |
| B. | egl always rises in the direction of flow |
| C. | egl always remains constant in the direction of flow |
| D. | egl may or may not in the direction of flow |
| Answer» A. egl always drops in the direction of c | |
| Explanation: egl is obtained by plotting total head at various points along the axis of the pipe. since the total head decreases in the direction of flow, egl will always drop in that direction. | |
| 15. |
Which of the following is true? |
| A. | hgl always drops in the direction of flow |
| B. | hgl always rises in the direction of flow |
| C. | hgl always remains constant in the direction of flow |
| D. | hgl may or may not in the direction of flow |
| Answer» D. hgl may or may not in the direction of flow | |
| Explanation: hgl is obtained by plotting piezometric head at various points along the axis of the pipe. since pressure may either rise or fall in the direction of flow, hgl may or may not change in that direction. | |
| 16. |
Which of the following is true? |
| A. | hgl will never be above egl |
| B. | hgl will never be under egl |
| C. | hgl will never coincide with egl |
| D. | hgl will may or may not be above egl |
| Answer» A. hgl will never be above egl | |
| Explanation: egl is obtained by plotting total head and hgl is obtained by plotting piezometric head at various points along the axis of the pipe. | |
| 17. |
The slope of HGL will be |
| A. | greater than that of egl for a pipe of uniform cross-section |
| B. | smaller than that of egl for a pipe of uniform cross-section |
| C. | equal than that of egl for a pipe of uniform cross-section |
| D. | independent of that of egl for a pipe of uniform cross-section |
| Answer» C. equal than that of egl for a pipe of uniform cross-section | |
| Explanation: the vertical intercept between egl and hgl is equal to the kinetic head. for a pipe of uniform cross-section, there will be no change in the velocity of flow across | |
| 18. |
For a nozzle, the vertical intercept between EGL and HGL |
| A. | increases |
| B. | decreases |
| C. | remains constant |
| D. | may increase or decrease |
| Answer» A. increases | |
| Explanation: the vertical intercept between egl and hgl is equal to the kinetic head. for a nozzle, the cross-sectional area decreases in the direction of flow leading to | |
| 19. |
between EGL and HGL |
| A. | increases |
| B. | decreases |
| C. | remains constant |
| D. | may increase or decrease |
| Answer» B. decreases | |
| Explanation: the vertical intercept between egl and hgl is equal to the kinetic head. for a diffuser, the cross-sectional area increases in the direction of flow leading to a decrease in the velocity of flow across the pipe. since the kinetic head decreases, the vertical intercept between egl and hgl will decrease. | |
| 20. |
Which of the following is true? |
| A. | the slope of egl will always be greater than that of the axis of the pipe |
| B. | the slope of egl will always be smaller than that of the axis of the pipe |
| C. | the slope of egl will always be equal to that of the axis of the pipe |
| D. | the slope of egl will always be independent of that of the axis of the pipe |
| Answer» D. the slope of egl will always be independent of that of the axis of the pipe | |
| Explanation: egl is obtained by plotting total head at various points along the axis of the pipe. | |
| 21. |
the pressure vary with the length of the pipe? |
| A. | linearly |
| B. | parabolic |
| C. | exponential |
| D. | constant |
| Answer» A. linearly | |
| Explanation: in a zero acceleration fully- developed flow in a pipe, the pressure gradually decreases linearly along the length of the pipe. hence, the pressure variation is said to be linear. | |
| 22. |
When a problem states “The velocity of the water flow in a pipe is 20 m/s”, which of the following velocities is it talking about? |
| A. | rms velocity |
| B. | average velocity |
| C. | absolute velocity |
| D. | relative velocity |
| Answer» B. average velocity | |
| Explanation: in a pipe-flow, the velocity is always referred to the average velocity. there may be a case where all water particles move in the same direction with 20 m/s, then the average velocity will be equal to absolute velocity. but, this is only a special case. | |
| 23. |
Which of the factors primarily decide whether the flow in a circular pipe is laminar or turbulent? |
| A. | the prandtl number |
| B. | the pressure gradient along the length of the pipe |
| C. | the dynamic viscosity coefficient |
| D. | the reynolds number |
| Answer» D. the reynolds number | |
| Explanation: high reynolds number flows | |
| 24. |
How is Reynolds number defined as? |
| A. | ratio of pressures in the inlet to the outlet of a pipe |
| B. | the product of velocity of the flow and the diameter of the pipe, divided by the kinematic viscosity of fluid |
| C. | the product of density of the fluid, velocity of the flow and the diameter of the pipe, divided by the dynamic viscosity of fluid |
| D. | ratio of inertia force to viscous force |
| Answer» D. ratio of inertia force to viscous force | |
| Explanation: the question demands the definition and not the commonly used formula of reynolds number. some of them denote the formula of reynolds number. the definition of reynolds number is the ratio of inertia force to viscous force in a pipe flow. | |
| 25. |
A circular pipe of radius 7 cm is used for water flow transmission. This pipe is moulded into another pipe with a square cross-section keeping the length same. (Ignore the thickness of the pipe). Calculate the hydraulic diameter of the moulded pipe. (Take π = 22/7). |
| A. | 11 cm |
| B. | 7 cm |
| C. | 3.5 cm |
| D. | 22 cm |
| Answer» A. 11 cm | |
| Explanation: the perimeter of the circular cross section and the square cross section will remain the same. perimeter = 44 cm. side of square = 11 cm. hydraulic diameter dh of | |
| 26. |
The Reynolds number is found out for a flow in a circular pipe. This circular pipe is moulded into a square pipe, keeping length of the pipe same. Ignore the thickness of the pipe. The Reynolds number changes by |
| A. | 57% decrease |
| B. | 57% increase |
| C. | 43% decrease |
| D. | 43% increase |
| Answer» B. 57% increase | |
| Explanation: the reynolds number directly depends upon the hydraulic diameter of the pipe. suppose the diameter of the pipe is d, the hydraulic diameter of square pipe is 1.57d. hence, 57% increase. | |
| 27. |
The flow through a circular pipe is laminar. Now, the fluid through the pipe is replaced with a more viscous fluid and passed through the pipe again with the same velocity. What can we say about the nature of this flow? |
| A. | the flow will become turbulent |
| B. | the flow will be a transition flow |
| C. | the flow will remain laminar |
| D. | the reynolds number of the earlier flow is required to answer this question |
| Answer» C. the flow will remain laminar | |
| Explanation: a flow through a circular pipe is said to be laminar when the reynolds | |
| 28. |
What can be the maximum diameter of the pipe for the water flow of velocity 1 m/s (ν = 10-6) to be laminar in nature? Assume Lower critical Reynolds number to be 2100. |
| A. | 2.1 mm |
| B. | 21 mm |
| C. | 21 cm |
| D. | 0.21 mm |
| Answer» A. 2.1 mm | |
| Explanation: if the reynolds number of the flow is below its lower critical reynolds number, the flow is clearly laminar. the maximum diameter can be found for re = 2100. the diameter comes out to be 2.1 mm. | |
| 29. |
Which of the following flows have the highest critical Reynolds number (lower)? |
| A. | flow in a pipe |
| B. | flow between parallel plates |
| C. | flow in an open channel |
| D. | flow around spherical body |
| Answer» A. flow in a pipe | |
| Explanation: the approximate lower critical reynolds number for flow in a pipe, flow between parallel plates, flow in an open channel and flow around the spherical body are 2000, 1000, 500 and 1 respectively. | |
| 30. |
The flow separation occurs when the fluid travels away from the |
| A. | surface |
| B. | fluid body |
| C. | adverse pressure gradient |
| D. | inter-molecular spaces |
| Answer» C. adverse pressure gradient | |
| Explanation: adverse pressure gradient takes place when the static pressure increases. it increases the direction of the flow. adverse pressure gradient plays an important role in flow separation. thus, option c is correct. | |
| 31. |
The swirl caused due to eddies are called as |
| A. | vortices |
| B. | vertices |
| C. | volume |
| D. | velocity |
| Answer» A. vortices | |
| Explanation: vortices are a region in a fluid. it takes place when the flow revolves around an axis line. vortices can be straight or curved. they form shapes like smoke rings and whirlpools. | |
| 32. |
Eddy viscosity is a turbulent transfer of |
| A. | fluid |
| B. | heat |
| C. | momentum |
| D. | pressure |
| Answer» C. momentum | |
| Explanation: eddy viscosity is a turbulent transfer of momentum by eddies. it gives rise to an internal fluid friction. it is in analogous to the action of molecular viscosity in laminar fluid flow. eddy viscosity takes place on a large scale. | |
| 33. |
Which among the following is a device that converts a laminar flow into a turbulent flow? |
| A. | dead weight gauge |
| B. | vacuum gauge |
| C. | turbulator |
| D. | ionization gauge |
| Answer» C. turbulator | |
| Explanation: turbulator is a device that converts a laminar flow into a turbulent flow. the turbulent flow can be desired parts of an aircraft or also in industrial applications. | |
| 34. |
Boundary layer separation does not undergo detachment. |
| A. | true |
| B. | false |
| Answer» B. false | |
| Explanation: boundary layer separation undergoes detachment from the surface into a broader wake. it occurs mainly when the portion of the boundary layer is closest to the wall. it leads to reverse in the flow direction. | |
| 35. |
With the boundary layer separation, displacement thickness |
| A. | increases |
| B. | decreases |
| C. | remains same |
| D. | independent |
| Answer» A. increases | |
| Explanation: with the boundary layer separation, displacement thickness increases sharply. this helps to modify the outside potential flow and its pressure field. thus, option ‘a’ is the correct choice. | |
| 36. |
automatic control scheme during the fluid flow? |
| A. | rotameters |
| B. | pulley plates |
| C. | rotary piston |
| D. | pilot static tube |
| Answer» D. pilot static tube | |
| Explanation: pilot static tube is a system that uses an automatic control scheme to detect pressure. it has several holes connected to one side of the device. these outside holes are called as a pressure transducer, which | |
| 37. |
What is D’Alembert’s Paradox? |
| A. | resistance= 0 |
| B. | drag force= 0 |
| C. | temperature = 0 |
| D. | pressure gradient= 0 |
| Answer» B. drag force= 0 | |
| Explanation: d’alembert’s paradox states that for an incompressible and inviscid flow potential flow, the drag force is equal to zero. the fluid is moving at a constant velocity with respect to its relative fluid. | |
| 38. |
The steady- state flow must satisfy |
| A. | kirchhoff’s law |
| B. | newtons law |
| C. | rutherford’s experiment |
| D. | kepler’s law |
| Answer» A. kirchhoff’s law | |
| Explanation: the steady state flow must satisfy kirchhoff’s first and second law. the first law states that the total flow into the junction equals the total flow away from the junction. second law is called as the law of conservation of mass. it states that between two junctions, the head loss is independent of the path followed. | |
| 39. |
depend on the friction factor? |
| A. | pipe diameter |
| B. | fluid density |
| C. | viscosity |
| D. | weight |
| Answer» D. weight | |
| Explanation: the friction factor(f) depends on the velocity of flow, fluid density, pipe diameter and the viscosity of the pipe. | |
| 40. |
How do we calculate losses for a larger range of Reynolds number? |
| A. | moody chart |
| B. | bar chart |
| C. | scatter chart |
| D. | column histogram |
| Answer» A. moody chart | |
| Explanation: moody chart is a graph of frictional factor(f) vs reynolds numbers. it gives various values corresponding to the | |
| 41. |
Darcy- Weisbach equation gives relation between |
| A. | pressure and temperature |
| B. | mass, volume and pressure |
| C. | head loss and pressure loss |
| D. | pressure loss only |
| Answer» C. head loss and pressure loss | |
| Explanation: darcy-weisbach equation relates the head loss and pressure loss due to friction along a given pipe with a specified length. it contains a dimensionless friction factor called the darcy friction factor. the equation was named after henry darcy and julius weisbach. | |
| 42. |
Which among the following is formula for friction factor of circular pipes? |
| A. | 16/re |
| B. | 64/re |
| C. | re/16 |
| D. | re/64 |
| Answer» B. 64/re | |
| Explanation: circular pipes have a diameter treated in a round manner. for a fluid flow which is laminar head loss is directly proportional to the fluid velocity. thus, friction factor is inversely proportional to its velocity. therefore, the correct option is ‘64/re’. | |
| 43. |
Loss of head due to friction is |
| A. | directly proportional to hydraulic radius |
| B. | inversely proportional to velocity |
| C. | inversely proportional to hydraulic radius |
| D. | directly proportional to gravitational constant |
| Answer» C. inversely proportional to hydraulic radius | |
| Explanation: hydraulic radius is one of the properties of a fluid flow in a channel. it controls the water discharge. it also determines the amount of work the channel | |
| 44. |
The formula for hydraulic diameter is |
| A. | 4a/p |
| B. | 4ap |
| C. | 4av |
| D. | 4v |
| Answer» A. 4a/p | |
| Explanation: hydraulic diameter handles the flow in non-circular channels and tubes. the most suitable term to calculate the hydraulic diameter for a round tube is dh= 4a/p. where ‘a’ is the cross-sectional area and ‘p’ is the wetted perimeter. | |
| 45. |
What are the reasons for minor head loses in a pipe? |
| A. | friction |
| B. | heat |
| C. | valves and bends |
| D. | temperature |
| Answer» C. valves and bends | |
| Explanation: minor losses play an important role in calculating the flow, pressure and energy of the piping system. fluid that moves through the pipe carries momentum and energy due to the forces acting on them. | |
| 46. |
What happens to the head loss when the flow rate is doubled? |
| A. | doubles |
| B. | same |
| C. | triples |
| D. | four times |
| Answer» D. four times | |
| Explanation: if the flow rate is doubled, the head loss increases by a factor of four. since, the head loss is directly proportional to the square of the flow rate. option (d) is the correct option. | |
| 47. |
Relative roughness is |
| A. | ϵ/d |
| B. | ϵ*d |
| C. | ϵ/dm |
| D. | ϵgd |
| Answer» A. ϵ/d | |
| Explanation: relative roughness is defined as the quantity used to measure the roughness | |
| 48. |
pipes can take up |
| A. | pipes of different diameters |
| B. | pipes of the same diameters only. |
| C. | single pipe only |
| D. | short pipes only |
| Answer» A. pipes of different diameters | |
| Explanation: when pipes of different diameters are connected at its ends to form a pipe, this pipe so developed is called as pipes in series. they might not have to be of the same diameters. but, having the same diameters are better as it avoids the losses so developed. | |
| 49. |
What is the total loss developed in a series of pipes? |
| A. | sum of losses in each pipe only |
| B. | sum of local losses only |
| C. | sum of local losses plus the losses in each pipe |
| D. | zero |
| Answer» C. sum of local losses plus the losses in each pipe | |
| Explanation: when the pipes of different diameters are connected in series from end to end to form a pipe line. the total loss so developed is equal to the sum of local losses | |
| 50. |
The total head loss for the system is equal to |
| A. | pipe length |
| B. | pipe diameter |
| C. | width of the reservoir |
| D. | height difference of reservoirs |
| Answer» D. height difference of reservoirs | |
| Explanation: total head loss for a system is equal to the height difference of the reservoirs. height difference is denoted by the letter ‘h’. total head loss can be equated | |
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