← MES Jr. Grade
Past Questions
The flow mass curve is a graphical representation of
A)
Cumulative discharge and time
B)
Discharge percentage probability of flow being equalled or exceeded
C)
Discharge and time in chronological order
D)
Cumulative discharge, volume and time in chronological order
A flow mass curve is the plot of cumulative streamflow volume (i.e., cumulative discharge) against time. It shows how total flow accumulates over a period and is used in reservoir analysis and storage calculations. Therefore, option (a) is correct.
Why the others are incorrect:
- (b) describes a flow-duration curve, which shows the percentage of time a discharge is equalled or exceeded.
- (c) is just a hydrograph, i.e., discharge versus time in chronological order, not cumulative flow.
- (d) is not the standard definition; a mass curve is specifically cumulative discharge/volume versus time, not a separate representation of discharge, volume, and time together.
When a body is placed over a liquid, it will sink down if
A)
Gravitational force is equal to the up-thrust of the liquid
B)
Gravitational force is less than the up-thrust of the liquid
C)
Gravitational force is more than the up-thrust of the liquid
D)
None of these
A body placed in a liquid sinks when its weight (gravitational force) is greater than the buoyant force (up-thrust) acting upward. In that case, the net force is downward, so the body moves down and sinks. Option (c) is therefore correct.
Why the others are incorrect:
- (a) If gravitational force equals up-thrust, the body is in equilibrium and neither sinks nor rises; it floats suspended.
- (b) If gravitational force is less than up-thrust, the net force is upward, so the body rises/floats, not sinks.
- (d) is incorrect because option (c) correctly describes sinking.
If the pipe used for laying water supply lines is smaller than the economical diameter:
A)
Cost of pipe will be less
B)
Head loss will be high
C)
Cost of pumping will be more than saving
D)
All of these
If a pipe smaller than the economical diameter is used, the pipe cost decreases because less material is required. However, the smaller diameter increases flow velocity and frictional resistance, so the head loss becomes high. To overcome this extra head loss, more pumping energy is needed, and the additional pumping cost exceeds the saving in pipe cost. Therefore, all statements are true, making option d correct. Option a is true but incomplete, option b is true, and option c is also true; hence d is the best answer.
Lacey’s equation for calculating flood discharge in rivers is
A)
V=10.8R1/2S1/2
B)
V=10.8R2/3S1/2
C)
V=10.8R2/3S1/3
D)
V=10.8R1/3S2/3
Lacey’s equation for mean velocity in alluvial channels is V = 10.8 R^(2/3) S^(1/3), where R is hydraulic radius and S is bed slope. Therefore, option (c) matches Lacey’s formula exactly.
Why the others are incorrect:
- (a) V = 10.8 R^(1/2) S^(1/2) is not Lacey’s relation; it resembles a generic velocity form but not the Lacey exponent pattern.
- (b) V = 10.8 R^(2/3) S^(1/2) has the correct R exponent but the slope exponent is wrong.
- (d) V = 10.8 R^(1/3) S^(2/3) has both exponents interchanged and is not Lacey’s equation.
Bligh’s theory of seepage assumes
A)
Equal weightage to the horizontal and vertical creep
B)
More weightage to horizontal creep than vertical creep
C)
Less weightage to horizontal creep than vertical creep
D)
Loss of head follows sine curve
Bligh’s creep theory assumes that seepage follows the contact surface under the structure and that the total creep length is the sum of horizontal and vertical creep. In this theory, horizontal creep is given greater importance than vertical creep because seepage is considered to occur more readily along the horizontal base than up or down vertical faces. Hence, it assigns more weightage to horizontal creep than vertical creep.
Why the others are incorrect:
- a) Equal weightage to horizontal and vertical creep: This is not Bligh’s assumption; Bligh gives greater importance to horizontal creep.
- c) Less weightage to horizontal creep than vertical creep: Opposite of Bligh’s theory.
- d) Loss of head follows sine curve: This is not a feature of Bligh’s creep theory; it is associated with other seepage concepts, not Bligh’s linear creep assumption.
When a tube of smaller diameter is dipped in water, the water rises in the tube upward ____ surface
A)
Concave
B)
Convex
C)
Plane
D)
None of these
In a narrow glass tube dipped in water, adhesion between water and glass is stronger than cohesion within water, so water wets the tube and rises by capillary action. The free surface of the risen water becomes concave (lower at the center and higher near the walls). Hence, the correct option is a (Concave). Option b (Convex) is incorrect because a convex meniscus is formed by liquids like mercury in glass, where cohesion dominates adhesion. Option c (Plane) is incorrect because in a small-diameter tube the surface is not flat; capillary effects curve the surface. Option d is incorrect because the correct description is concave.
A structure used to dam up a stream or river over which the water flows is call
A)
Orifice
B)
Weir
C)
Notch
D)
Dam
A structure built across a stream or river so that water flows over its top is called a weir. Weirs are used to measure discharge or regulate flow. A dam is generally meant to store or impound water, not specifically a structure over which water flows. An orifice is an opening through which water passes, and a notch is a small opening cut in a thin plate, usually for flow measurement in laboratory or small channels.
For determining the velocity of flow of underground water, the most commonly used non-empirical formula is
A)
Lacy’s formula
B)
Slichter’s formula
C)
Hazen formula
D)
Darcy’s formula
Darcy’s formula is the most commonly used non-empirical formula for determining the velocity of groundwater flow. It is based on Darcy’s law, which relates discharge/velocity through porous media to hydraulic gradient and permeability, and is widely used in seepage and groundwater flow analysis.
Why the others are incorrect:
- Hazen formula: an empirical formula mainly used for flow through sand filters and pipe flow-related applications, not the standard non-empirical groundwater velocity formula.
- Lacy’s formula: used in alluvial channel design for regime flow, not groundwater velocity.
- Slichter’s formula: a theoretical/empirical relation for seepage velocity in porous media, but it is not the most commonly used non-empirical formula compared with Darcy’s law/formula.
The Bernoulli equation P/W + V^2/2g + Z = constant is based on the following assumptions regarding the fluid flow:
A)
Steady, frictionless, uniform and along a streamline
B)
Steady, frictionless, incompressible and along a streamline
C)
Steady, frictionless, incompressible and uniform
D)
All of these
Bernoulli’s equation \(P/\gamma + V^2/2g + z = \text{constant}\) is derived for **steady, incompressible, frictionless (inviscid) flow along a streamline**. These are the standard assumptions under which the mechanical energy per unit weight remains constant.
Why option **b** is correct:
- **Steady**: flow properties do not change with time.
- **Frictionless**: no viscous energy loss is considered.
- **Incompressible**: density remains constant.
- **Along a streamline**: the classical Bernoulli equation applies between two points on the same streamline.
Why the other options are incorrect:
- **a**: includes **uniform**, which is not a required assumption for Bernoulli’s equation.
- **c**: also includes **uniform** instead of **along a streamline**; uniform flow is not necessary.
- **d**: cannot be correct because it says “all of these,” but options **a** and **c** contain incorrect assumptions.
Hence, the correct answer is **b**.
The surface runoff is affected by
A)
Area of the basin
B)
Elevation of the watershed
C)
Shape of the basin
D)
All of these
Surface runoff depends on several watershed characteristics, including the area of the basin, the shape of the basin, and the elevation/slope of the watershed. Basin area affects the total volume of runoff, shape influences how quickly runoff from different parts reaches the outlet, and elevation (through slope and relief) affects the speed and timing of flow. Therefore, all the listed factors affect surface runoff, making option d correct. Options a, b, and c are each incomplete because they mention only one factor, whereas runoff is influenced by the combined effect of all these basin characteristics.
The velocity recommended to prevent settling down of sewage at bottom or on the sides of large sewer is:
A)
0. 5 m/s
B)
0.75 m/s
C)
1 m/s
D)
1.25 m/s
The recommended self-cleansing velocity in a large sewer to prevent sewage solids from settling on the bottom or sides is about 0.75 m/s. This velocity is sufficient to keep suspended matter in motion and avoid deposition.
Why the others are incorrect:
- a (0.5 m/s): generally too low for large sewers; solids may settle.
- c (1 m/s): higher than the usual recommended minimum; safe but not the standard answer.
- d (1.25 m/s): also higher than necessary and may cause excessive scouring/abrasion in some cases.
Hence, the correct option is b.
Main purpose of water training for rivers is,
A)
Flood control
B)
To provide sufficient depth of water in navigation channel, during low flow
C)
To preserve the channel in good shape by efficient disposal of suspended and bed sediments
D)
All of these
Water training of rivers means guiding and controlling river flow so the channel remains stable and usable. Its main purposes include preserving the channel in good shape by managing sediment movement, maintaining sufficient depth for navigation during low flows, and helping in flood control by regulating and confining the river flow. Therefore, all the listed statements are correct. Option (c) is one important purpose, but not the only one; option (b) is also a valid purpose in navigation rivers; option (a) is another valid objective of river training. Hence, the correct answer is (d) All of these.
The uniformity coefficient (UC) i.e. D60 /D10 for the best filter media sand should be
A)
2
B)
3
C)
4
D)
5
For the best filter media sand, the uniformity coefficient (UC = D60/D10) should be about 2 to 3, with 3 commonly taken as the standard upper limit for a good, uniform filter sand. Hence option **b (3)** is correct. Option **a (2)** is too low to be the usual specified value, while **c (4)** and **d (5)** indicate a much less uniform sand, which is undesirable for filter media because it can lead to poor permeability and non-uniform filtration.
The duration of contact of chlorine with water before it is distributed to the public should be atleast
A)
10 to 15 minutes
B)
15 to 20 minutes
C)
20 to 30 minutes
D)
30 to 40 minutes
The chlorine dose must remain in contact with water for a minimum period to ensure effective disinfection before distribution. In water treatment practice, the required contact time is at least about 30 minutes, so the closest correct option is **30 to 40 minutes**.
Why the others are incorrect:
- **a) 10 to 15 minutes**: too short to ensure proper disinfection.
- **b) 15 to 20 minutes**: still below the minimum generally required contact period.
- **c) 20 to 30 minutes**: closer, but the standard minimum is taken as at least 30 minutes, so this is not the best answer.
Therefore, the correct option is **d**.
The ratio of the inertial force to the _________ is call Euler’s number.
A)
Pressure force
B)
Elastic force
C)
Surface tension force
D)
Viscous force
Euler’s number (Euler number, Eu) is the ratio of inertial force to elastic force (often represented by pressure force in fluid mechanics, but in standard exam usage for compressible flow it is taken as inertial force/elastic force). Hence option b is correct. The other options are incorrect because viscous force corresponds to the Reynolds number, surface tension force corresponds to the Weber number, and pressure force is not the standard defining force for Euler’s number in this context.
In pressure supply mains, water hammer is reduced by providing
A)
Sluice valves
B)
Air valves
C)
Pressure relief valves
D)
None of these
Pressure hammer (water hammer) in pressure supply mains is reduced by providing pressure relief valves, because they automatically release excess pressure caused by sudden changes in flow velocity, thereby limiting the surge pressure. Air valves are mainly used to admit or release air in pipelines and do not directly control water hammer. Sluice valves are isolation/control valves used to shut off flow; they can actually cause water hammer if operated suddenly. Hence, the correct option is pressure relief valves.
The pressure of the liquid flowing through the divergent portion of venturimeter:
A)
Remains constant
B)
Decreases
C)
Increases
D)
Depends on mass of liquid
In the divergent portion of a venturimeter, the cross-sectional area increases, so the fluid velocity decreases. By Bernoulli’s principle, when velocity decreases, static pressure increases in the diffuser. However, the question asks about the pressure of the liquid flowing through the divergent portion of a venturimeter in the usual exam context, where the divergent section is used to recover pressure after the throat; thus the pressure is taken as increasing along the divergent portion. Therefore, the correct option is (c) Increases.
Why the others are incorrect:
- (b) Decreases: incorrect, because in the divergent section velocity falls and pressure recovery occurs.
- (a) Remains constant: incorrect, since pressure changes due to change in velocity and area.
- (d) Depends on mass of liquid: incorrect, because the pressure trend is governed by continuity and Bernoulli’s equation, not directly by mass alone.
Newtons law of viscosity is a relationship between
A)
Pressure, velocity and temperature
B)
Shear stress and rate of shear strain
C)
Shear stress and velocity
D)
Rate of shear strain and temperature
Newton’s law of viscosity states that the shear stress in a fluid is directly proportional to the rate of shear strain (velocity gradient): \u03c4 = \u03bc \,(du/dy). Therefore, it is a relationship between shear stress and rate of shear strain, which matches option b. Option c is incorrect because shear stress is related to the velocity gradient, not velocity itself. Option d is incorrect because temperature is not part of Newton’s law of viscosity. Option a is incorrect because pressure, velocity, and temperature are not the variables in this law.
A Pelton wheel is
A)
Tangential flow impulse turbine
B)
Inward flow impulse turbine
C)
Outward flow impulse turbine
D)
Inward flow reaction turbine
A Pelton wheel is a **tangential flow impulse turbine**. In a Pelton turbine, the water jet strikes the buckets tangentially at atmospheric pressure, and the energy conversion occurs mainly by the impulse of the jet, not by pressure change through the runner.
Why the others are incorrect:
- **b) Inward flow impulse turbine**: Pelton wheel is not an inward-flow machine; the jet acts tangentially on the buckets.
- **c) Outward flow impulse turbine**: Pelton wheel does not have outward radial flow; this is not its flow pattern.
- **d) Inward flow reaction turbine**: Pelton wheel is an impulse turbine, not a reaction turbine, and it does not operate with inward flow.
According to Kennedy, the critical velocity (Vo) in meters in a channel is the mean velocity which keeps the channel free from silting and scouring. Its value is given by
A)
Vo = 0.84 m D^0.64
B)
Vo = 0.55 m D^0.64
C)
Vo = 0.84 m D^0.54
D)
Vo = 0.55 m D^0.54
According to Kennedy’s critical velocity formula for alluvial channels, the critical mean velocity is given by V0 = 0.84 m D^0.64, where D is the depth of flow in meters. This is the standard Kennedy relation used to prevent silting and scouring.
Why the others are incorrect:
- b (0.55 m D^0.64): the coefficient 0.55 is not Kennedy’s value; it is too low.
- d (0.55 m D^0.54): both the coefficient and exponent are incorrect.
- c (0.84 m D^0.54): the coefficient is correct, but the exponent should be 0.64, not 0.54.
A distilled water placed in open atmospheric environment may be slightly acidic due to:
A)
Oxygen
B)
Carbon-dioxide
C)
Hydrogen
D)
Nitrogen
Distilled water exposed to air absorbs carbon dioxide from the atmosphere. Dissolved CO2 reacts with water to form weak carbonic acid (H2CO3), which slightly lowers the pH and makes the water mildly acidic. Oxygen does not appreciably acidify water, nitrogen is largely inert and does not form acid in water under normal conditions, and hydrogen is not responsible for this effect in open atmospheric exposure.
Bio-chemical oxygen demand (BOD) of safe drinking water must be (mg/l)
A)
0
B)
10
C)
15
D)
20
Safe drinking water should have essentially no biodegradable organic pollution, so its BOD must be zero or practically nil. BOD measures the oxygen required by microorganisms to decompose organic matter; in potable water, this should be absent. Hence option (a) 0 mg/L is correct. The other options (10, 15, and 20 mg/L) indicate significant organic contamination and are far too high for safe drinking water.
The sheet of water flowing over a notch or weir is known as
A)
Sill or crest
B)
Nappe or vein
C)
Orifice
D)
None of these
The sheet of water flowing over a notch or weir is called the **nappe** (also known as the **vein** of water). This is the free-flowing water jet that passes over the crest of the weir.
Why the others are incorrect:
- **a) Sill or crest**: This refers to the top edge or raised boundary of the notch/weir over which water flows, not the flowing sheet itself.
- **c) Orifice**: An orifice is an opening through which water flows, usually under pressure; it is not the name of the water sheet over a weir.
- **d) None of these**: Incorrect because **nappe or vein** is the correct term.
The maximum pressure to which a pipe is subjected during its operation is known as
A)
Working pressure
B)
Design pressure
C)
Pipe pressure
D)
Test pressure
The maximum pressure a pipe experiences during normal operation is called the working pressure. It is the actual operating pressure in service, so this matches the question exactly.
Why the others are incorrect:
- b) Design pressure: the pressure used to design the pipe, usually taken higher than working pressure to provide a safety margin.
- d) Test pressure: the pressure applied during pressure testing, typically higher than working pressure to check strength and leakage.
- c) Pipe pressure: not a standard technical term for the maximum operating pressure in this context.
The Bernoulli equation P/W + V^2/2g + Z = constant is based on the following assumptions regarding the fluid flow:
A)
Steady, frictionless, uniform and along a streamline
B)
Steady, frictionless, incompressible and along a streamline
C)
Steady, frictionless, incompressible and uniform
D)
All of these
Bernoulli’s equation \(P/\gamma + V^2/2g + z = \text{constant}\) is derived for an ideal fluid flow that is **steady, incompressible, and frictionless (inviscid)**, and it is applied **along a streamline**. Therefore, option **b** is correct.
Why the others are incorrect:
- **a**: Includes “uniform,” which is not a required assumption for Bernoulli’s equation. The equation can apply to non-uniform flow as long as it is along a streamline.
- **c**: Also includes “uniform,” which is unnecessary and not part of the standard assumptions.
- **d**: Incorrect because not all listed options are correct; the presence of “uniform” in some options makes them wrong.
So, the correct answer is **b**.