← MES Jr. Grade
Past Questions
When a body floating in a liquid is displaced slightly, it oscillates about
A)
C.G of body
B)
Centre of pressure
C)
Centre of buoyancy
D)
Metacentre
A floating body given a small displacement oscillates about the metacentre. For a floating body, the metacentre is the point about which the body has stable angular oscillations for small tilts; if the metacentre lies above the centre of gravity, the body returns to its original position.
Why others are incorrect:
- a) C.G. of body: The centre of gravity is the point where the weight acts, but the oscillation of a floating body is not about this point.
- b) Centre of pressure: This is used for hydrostatic force on submerged surfaces, not for the oscillation of floating bodies.
- c) Centre of buoyancy: This is the centroid of the displaced liquid volume, and it shifts when the body tilts; the body does not oscillate about it.
The units of Alkalinity is express as mg/l in terms of equivalent
A)
Calcium carbonate
B)
Magnesium carbonate
C)
Sodium carbonate
D)
Calcium hydroxide
Alkalinity in water analysis is conventionally reported as mg/L as CaCO3 (calcium carbonate). This is because CaCO3 is the standard reference substance used to express acid-neutralizing capacity on an equivalent basis. Therefore, the correct option is calcium carbonate.
Why the others are incorrect:
- Sodium carbonate: can contribute to alkalinity, but it is not the standard reporting basis.
- Magnesium carbonate: also alkaline, but not the conventional equivalent unit used in water chemistry.
- Calcium hydroxide: a strong base that can cause alkalinity, but alkalinity is still expressed as mg/L as CaCO3, not as Ca(OH)2.
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**.
The self-cleansing velocity recommended for Indian conditions, in order 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 for large sewers under Indian conditions is about 0.75 m/s. This velocity is sufficient to keep sewage solids in suspension and prevent deposition at the bottom or sides of the sewer.
Why the other options are incorrect:
- 0.5 m/s is generally too low for reliable self-cleansing in large sewers, so settling may occur.
- 1.0 m/s is higher than the usual recommended minimum and is not the standard value asked for in Indian conditions.
- 1.25 m/s is unnecessarily high as a minimum self-cleansing velocity and is not the commonly recommended figure.
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.
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.
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.
For standing crops in undulating sandy fields the best method of irrigation is
A)
Sprinkler irrigation
B)
Free flooding
C)
Check method
D)
Furrow method
Sprinkler irrigation is the best method for standing crops in undulating sandy fields because it applies water uniformly like rainfall, works well on uneven land where leveling is difficult, and is suitable for sandy soils that have high infiltration and low water-holding capacity. It also reduces runoff and water loss compared with surface methods.
Why the others are incorrect:
- Check method: Suitable for level fields and paddy-like conditions, not for undulating sandy land.
- Furrow method: Better for row crops on fairly level land with moderate infiltration; on sandy soils water may percolate too quickly and distribution becomes poor.
- Free flooding: Wasteful and uncontrolled, causing uneven application and runoff, especially unsuitable for undulating terrain.
The property by virtue of which liquid opposes relative motion between its different layer is called
A)
Viscosity
B)
Surface tension
C)
Compressibility
D)
All of these
The correct answer is **Viscosity**. Viscosity is the property of a liquid that causes it to resist the relative motion between its adjacent layers, i.e., internal friction within the fluid.
Why the others are incorrect:
- **Compressibility**: This is the property of a fluid to change its volume under pressure, not to oppose layer-to-layer motion.
- **Surface tension**: This is the property due to which the liquid surface behaves like a stretched membrane; it acts at the free surface, not between layers.
- **All of these**: Incorrect because only viscosity describes resistance to relative motion between fluid layers.
In rapid sand filter, air binding is caused due to excessive
A)
Negative pressure
B)
Positive pressure
C)
Turbidity
D)
Microbes
Air binding in a rapid sand filter occurs when excessive negative pressure (suction) develops in the filter bed, causing dissolved air to come out of solution and form air pockets that block flow. This is why option (a) is correct. Option (b) positive pressure is incorrect because it does not cause air to be released from water into the pores of the filter bed. Option (c) turbidity is the load of suspended matter and may clog the filter, but it does not specifically cause air binding. Option (d) microbes are related to biological activity in water, not to the formation of air pockets in the filter bed.
The process of passing water through beds of granular materials is called
A)
Filtration
B)
Coagulation
C)
Screening
D)
Sedimentation
Passing water through beds of granular material (such as sand, gravel, or anthracite) is called filtration. In this process, suspended and colloidal impurities are removed as water flows through the porous media. Coagulation is the chemical destabilization of fine particles before settling or filtration, screening is the removal of large floating debris by a mesh or bar screen, and sedimentation is the settling of heavier particles under gravity in a tank.
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 structure constructed to allow drainage water to flow under pressure through an inverted syphon below a canal, is called
A)
Syphon
B)
Super passage
C)
Super aquaduct
D)
Syphon aquaduct
A structure that carries drainage water under a canal in a closed conduit and allows it to flow under pressure is called a **syphon** (more specifically, an inverted syphon or syphon aqueduct arrangement depending on the relative levels). Here, the key idea is that the drainage passes **below the canal under pressure**, which matches a syphon.
Why the others are incorrect:
- **b) Super passage**: This is the opposite arrangement, where the canal water passes **over** the drainage channel.
- **c) Super aquaduct**: This is also an overcrossing arrangement, where the canal is carried **over** the drainage.
- **d) Syphon aquaduct**: This term is not the standard answer for this description in basic irrigation engineering MCQs; the correct general term for drainage flowing under pressure below a canal is **syphon**.
Irrigation canals are generally aligned along
A)
Ridge line
B)
Contour line
C)
Valley line
D)
Straight line
Irrigation canals are generally aligned along the ridge line (watershed line) so that water can be distributed by gravity to both sides of the canal command area. This also helps minimize cross-drainage problems and allows the canal to serve land on either side efficiently.
Why the others are incorrect:
- Contour line: canals may follow contours in hilly terrain, but the general and preferred alignment for irrigation canals is along the ridge line, not simply any contour.
- Valley line: valleys are natural drainage paths, so aligning a canal there would cause excessive crossing of drains and flooding issues.
- Straight line: canal alignment is governed by topography and command area, not by a straight geometric path.
Manometers are used to measure
A)
Pressure in water channel, pipes etc.
B)
Difference in pressure at two points
C)
Atmospheric pressure
D)
Very low pressure
Manometers are instruments used to measure pressure differences between two points, or between a point and the atmosphere. Hence option (b) is correct. Option (c) is incorrect because atmospheric pressure is measured by a barometer, not a manometer. Option (d) is incorrect because very low pressure is measured by a vacuum gauge or similar device. Option (a) is too specific and not the general definition; manometers can measure pressure in pipes or channels, but fundamentally they measure pressure difference.
The unit of kinematic viscosity is
A)
N-m/s
B)
N sec/m2
C)
m2/s
D)
N-m
Kinematic viscosity is defined as dynamic viscosity divided by density, so its SI unit is (N·s/m²)/(kg/m³) = m²/s. Therefore option c is correct. Option b (N·s/m²) is the unit of dynamic viscosity, not kinematic viscosity. Option a (N·m/s) is a unit of power, and option d (N·m) is a unit of work/energy, so both are incorrect.
Meandering pattern of a river a river is developed by
A)
Average discharge
B)
Dominant discharge
C)
Maximum discharge
D)
Critical dischage
Meandering pattern of a river is developed by the dominant discharge, i.e., the flow that occurs most frequently and is most effective in shaping the channel over time. This discharge controls the long-term geomorphic work of the river, including lateral erosion and deposition that produce meanders.
Why the others are incorrect:
- Average discharge: It is only a statistical mean and does not represent the flow condition that most strongly governs channel form.
- Maximum discharge: Flood flows are short-lived and mainly cause temporary scour or overbank flooding, not the persistent development of meanders.
- Critical discharge: This is a hydraulic concept related to flow regime (critical depth/velocity), not the discharge responsible for meander formation.
Which of the following methods of applying water may be used on rolling land
A)
Border flooding
B)
Check flooding
C)
Furrow flooding
D)
Free flooding
Furrow flooding is suitable for rolling or undulating land because water is applied in small channels (furrows) between crop rows, so the field does not need to be perfectly level. This makes it practical on sloping or rolling terrain.
Border flooding and check flooding generally require fairly level land and careful land shaping to retain and distribute water uniformly, so they are not preferred on rolling land. Free flooding is uncontrolled and inefficient, and it is also not suitable for uneven ground because water spreads irregularly and causes non-uniform irrigation.
A triangular notch is preferred to rectangular notch because
A)
Only one reading is required
B)
Its formula is simple to remember
C)
It gives more accurate results for low discharges
D)
All of these
A triangular notch is preferred over a rectangular notch mainly because it is more sensitive and gives more accurate measurement of small/low discharges. For low flows, the head over the notch can be measured more precisely, so the discharge calculation is better suited to small quantities of water.
Why the other options are incorrect:
- (a) Only one reading is required: This is not a special advantage of triangular notches; both notch types generally require head measurement.
- (b) Its formula is simple to remember: The triangular notch formula is not simpler than the rectangular notch in any meaningful practical sense, and this is not the reason for preference.
- (d) All of these: Incorrect because (a) and (b) are not valid reasons.
Removal of oil and grease from sewage, is known
A)
Screening
B)
Skimming
C)
Filtration
D)
None of these
The removal of oil and grease from sewage is called skimming. In this process, floating oils, fats, and grease are separated from the wastewater surface, usually in a skimming tank or grease trap. Screening is used to remove large floating and suspended solids, not oil and grease. Filtration is a treatment process for removing finer suspended particles by passing water through a porous medium, and it does not specifically refer to oil and grease removal. Therefore, the correct answer is skimming.
The consumptive use of water for a crop
A)
Is measured as the volume of water per unit area
B)
Is measured as depth of water on irrigated area
C)
May be supplied partly by precipitation and partly by irrigation
D)
All of these
Consumptive use of water for a crop is the total water used by the crop through evapotranspiration plus the water used in building plant tissue. It is commonly expressed as a depth of water over the irrigated area (e.g., cm or mm), which is equivalent to volume per unit area. Also, this demand can be met partly by effective precipitation and partly by irrigation. Therefore, all three statements are correct, so option d is right. Option a is correct because depth of water per unit area is the standard way to express consumptive use. Option b is correct because consumptive use is often represented as an equivalent depth on the irrigated field. Option c is correct because rainfall and irrigation can together satisfy the crop’s consumptive use.
Bacteria require free oxygen for their survival are called
A)
Facultative bacteria
B)
Pathogenic bacteria
C)
Anaerobic bacteria
D)
Aerobic bacteria
Bacteria that require free oxygen for survival are called aerobic bacteria. They use oxygen in respiration to obtain energy. Facultative bacteria can live with or without oxygen, anaerobic bacteria do not require oxygen and may even be harmed by it, and pathogenic bacteria are disease-causing bacteria, which is unrelated to oxygen requirement.
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 pH value of water for public water supplies is limited from
A)
2.5 to 6
B)
6.5 to 8
C)
7 to 8.5
D)
8 to 10
The pH of water for public water supply is generally kept within the acceptable range of about 6.5 to 8.0 (often stated as 6.5 to 8.5 in standards). This range is important because water below 6.5 becomes acidic and can cause corrosion of pipes, while water much above 8 becomes alkaline and may affect taste and treatment efficiency. Therefore, option b is the best match.
Why the others are incorrect:
- c (7 to 8.5): This is narrower and starts too high; public supply water need not be as high as 7, and the lower acceptable limit is typically 6.5.
- d (8 to 10): Too alkaline for potable water; such high pH is generally not acceptable for public supply.
- a (2.5 to 6): Far too acidic and completely unsuitable for public water supply.