Explore topic-wise MCQs in GATE (Mechanical Engineering).

This section includes 198 Mcqs, each offering curated multiple-choice questions to sharpen your GATE (Mechanical Engineering) knowledge and support exam preparation. Choose a topic below to get started.

51.

The jet ratio is defined as the ratio of the

A. diameter of jet to the diameter of Pelton wheel
B. velocity of jet to the velocity of Pelton wheel
C. diameter of Pelton wheel to the diameter of jet
D. velocity of Pelton wheel to the velocity of jet
Answer» D. velocity of Pelton wheel to the velocity of jet
52.

A Pelton wheel develops 1750 kW under a head of 100 metres while running at 200 r.p.m. and discharging 2500 litres of water per second. The unit speed of the wheel is

A. 10 r.p.m.
B. 20 r.p.m.
C. 40 r.p.m.
D. 80 r.p.m.
Answer» C. 40 r.p.m.
53.

A Francis turbine is an outward flow reaction turbine.

A. True
B. False
C. Can't say
D. None of these
Answer» C. Can't say
54.

Mechanical efficiency of a centrifugal pump is the ratio of

A. energy available at the impeller to the energy supplied to the pump by the prime mover
B. actual workdone by the pump to the energy supplied to the pump by the prime mover
C. energy supplied to the pump to the energy available at the impeller
D. manometric head to the energy supplied by the impeller per kN of water
Answer» B. actual workdone by the pump to the energy supplied to the pump by the prime mover
55.

The force exerted (in newton) by a jetof water impinging normally on a fixed plate is (where w = Specific weight of water in N/m³, a = Cross-sectional area of jet in m², and V = Velocity of jet in m/s)

A. waV / 2g
B. waV / g
C. waV² / 2g
D. waV² / g
Answer» E.
56.

The undershot water wheels are those in which

A. the wheel runs entirely by the weight of water
B. the wheel runs entirely by the impulse of water
C. the wheel runs partly by the weight of water and partly by the impulse of water
D. none of the above
Answer» C. the wheel runs partly by the weight of water and partly by the impulse of water
57.

The specific speed (Ns) of a centrifugal pump is given by

A. (N√Q)/H^2/3
B. (N√Q)/H^3/4
C. (N√Q)/H
D. (N√Q)/H5/4
Answer» C. (N√Q)/H
58.

The flow ratio in case of Francis turbine varies from

A. 0.15 to 0.3
B. 0.4 to 0.5
C. 0.6 to 0.9
D. 1 to 1.5
Answer» B. 0.4 to 0.5
59.

In a Francis turbine runner, the number of blades are generally between

A. 2 to 4
B. 4 to 8
C. 8 to 16
D. 16 to 24
Answer» E.
60.

The efficiency of a reaction turbine for a given head __________ with the increase in speed.

A. decreases
B. increases
C. Can't say
D. None of these
Answer» B. increases
61.

A jet of water is striking at the centre of a curved vane moving with a uniform velocity in the direction of jet. For the maximum efficiency, the vane velocity is __________ of the jet velocity

A. one-half
B. one-third
C. two-third
D. three-fourth
Answer» C. two-third
62.

The Thomson's turbine is __________ reaction turbine.

A. an axial flow
B. an inward flow
C. an outward flow
D. a mixed flow
Answer» C. an outward flow
63.

The runaway speed of a hydraulic turbine is the speed

A. at full load
B. at which there will be no damage to the runner
C. corresponding to maximum overload permissible
D. at which the turbine will run freely without load
Answer» E.
64.

The hydraulic efficiency of an impulse turbine is maximum when velocity of wheel is __________ of the jet velocity,

A. one-fourth
B. one-half
C. three-fourth
D. double
Answer» C. three-fourth
65.

A draft tube is used with impulse turbines.

A. Yes
B. No
C. Can't say
D. None of these
Answer» C. Can't say
66.

Which of the following pump is successfully used for lifting water to the turbines?

A. Centrifugal pump
B. Reciprocating pump
C. Jet pump
D. Air lift pump
Answer» D. Air lift pump
67.

For 450 m head of water, __________ shallbeused.

A. Pelton wheel
B. Kaplan turbine
C. Francis turbine
D. none of these
Answer» B. Kaplan turbine
68.

In a reaction turbine, the water enters the wheel under pressure and flows over the vanes.

A. Correct
B. Incorrect
C. Can't say
D. None of these
Answer» B. Incorrect
69.

The air vessel, in a reciprocating pump, is a cast iron closed chamber having an opening at its base.

A. Agree
B. Disagree
C. Can't say
D. None of these
Answer» B. Disagree
70.

By fitting an air vessel to the reciprocating pump, there is always a saving of work done and subsequently saving of power.The saving in case of a double acting reciprocating pump is

A. 39.2%
B. 48.8%
C. 84.8%
D. 88.4%
Answer» B. 48.8%
71.

Kinematic similarity is said to exist between the model and the prototype, if both of them

A. have identical velocities
B. are equal in size and shape
C. are identical in shape, but differ only in size
D. have identical forces
Answer» B. are equal in size and shape
72.

In an axial flow reaction turbine, the water flows __________ to the axis of the wheel.

A. parallel
B. perpendicular
C. Can't say
D. None of these
Answer» B. perpendicular
73.

The head available at the inlet of the turbine is known as net or effective head.

A. Correct
B. Incorrect
C. Can't say
D. None of these
Answer» B. Incorrect
74.

The power developed by a turbine is (where H = Head of water under which the turbine is working)

A. directly proportional to H^1/2
B. inversely proportional to H^1/2
C. directly proportional to H^3/2
D. inversely proportional to H^3/2
Answer» D. inversely proportional to H^3/2
75.

A hydraulic ram is a device used to

A. store the energy of water
B. increase the pressure of water
C. to lift water from deep wells
D. to lift small quantity of water to a greater height when a large quantity of water is available at a smaller height
Answer» E.
76.

The unit speed of the turbine runner is

A. N/√H
B. N/H
C. N/H^3/2
D. N/H²
Answer» B. N/H
77.

A hydraulic intensifier is a device used to increase the intensity of pressure of water by means of energy available from a large quantity of water at a low pressure.

A. Correct
B. Incorrect
C. Can't say
D. None of these
Answer» B. Incorrect
78.

The efficiency of jet propulsion for a ship with inlet orifices at right angles to the direction of motion of ship, will be maximum when the relative velocity of the jet and ship is equal to twice the velocity of the ship.

A. Yes
B. No
C. Can't say
D. None of these
Answer» B. No
79.

The efficiency of a hydraulic press is given by (where W = Weight lifted by ram, P = Force applied on plunger, A = Area of ram, and a = Area of plunger)

A. (W/p) × (A/a)
B. (p/W) × (a/A)
C. (W/p) × (a/A)
D. (p/W) × (A/a)
Answer» D. (p/W) × (A/a)
80.

Slip of a reciprocating pump is negative, when

A. suction pipe is short and pump is running at low speeds
B. delivery pipe is long and pump is running at high speeds
C. suction pipe is short and delivery pipe is long and the pump is running at low speeds
D. suction pipe is long and delivery pipe is short and the pump is running at high speeds
Answer» E.
81.

A Pelton wheel working under a constant head and discharge, has maximum efficiency when the speed ratio is

A. 0.26
B. 0.36
C. 0.46
D. 0.56
Answer» D. 0.56
82.

The working of which of the following hydraulic units is based on Pascal's law?

A. Air lift pump
B. Jet pump
C. Hydraulic coupling
D. Hydraulic press
Answer» E.
83.

A turbine develops 10000 kW under a head of 25 metres at 135 r.p.m. Its specific speed is

A. 175.4 r.p.m.
B. 215.5 r.p.m.
C. 241.5 r.p.m.
D. 275.4 r.p.m
Answer» D. 275.4 r.p.m
84.

In a mixed flow centrifugal pump, the flow through the impeller is a combination of radial and axial flows.

A. Correct
B. Incorrect
C. Can't say
D. None of these
Answer» B. Incorrect
85.

A reciprocating pump is suitable for less discharge and higher heads.

A. True
B. False
C. Can't say
D. None of these
Answer» B. False
86.

The ratio of the normal force of jet of water on a plate inclined at an angle of 30° as compared to that when the plate is normal to jet, is

A. 1/2
B. 1/2
C. 1
D. 2
Answer» D. 2
87.

Which of the following pump is generally used to pump highly viscous fluid?

A. Centrifugal pump
B. Reciprocating pump
C. Air lift pump
D. Screw pump
Answer» E.
88.

Dynamic similarity is said to exist between the model and the prototype, if both of them

A. have identical velocities
B. are equal in size and shape
C. are identical in shape, but differ only in size
D. none of the above
Answer» E.
89.

Delivery head of a centrifugal pump is

A. directly proportional to N
B. inversely proportional to N
C. directly proportional to N²
D. inversely proportional to N²
Answer» D. inversely proportional to N²
90.

Power required (in watts) to drive a centrifugal pump is (where Hm = Manometric head in metres, w = Specific weight in N/m³, Q = Discharge of the pump in m³/s, and ηo = Overall efficiency of the pump)

A. (w Hm) / (Q × ηo)
B. (w Hm Q) / ηo
C. (w Q) / (Hm × ηo)
D. (w Q ηo) / Hm
Answer» C. (w Q) / (Hm × ηo)
91.

The Furneyron turbine is __________ reaction turbine.

A. an axial flow
B. an inward flow
C. an outward flow
D. a mixed flow
Answer» D. a mixed flow
92.

The discharge through a turbine is

A. directly proportional to H^1/2
B. inversely proportional to H^1/2
C. directly proportional to H^3/2
D. inversely proportional to H^3/2
Answer» B. inversely proportional to H^1/2
93.

The cavitation in a hydraulic machine is mainly due to

A. low velocity
B. high velocity
C. low pressure
D. high pressure
Answer» D. high pressure
94.

Manometric head is the actual head of water against which a centrifugal pump has to work.

A. Correct
B. Incorrect
C. Can't say
D. None of these
Answer» B. Incorrect
95.

Overall efficiency of a centrifugal pump is the ratio of

A. energy available at the impeller to the energy supplied to the pump by the prime mover
B. actual workdone by the pump to the energy supplied to the pump by the prime mover
C. energy supplied to the pump to the energy available at the impeller
D. manometric head to the energy supplied by the impeller per kN of water
Answer» C. energy supplied to the pump to the energy available at the impeller
96.

Which of the following pump is suitable for small discharge and high heads?

A. Centrifugal pump
B. Axial flow pump
C. Mixed flow pump
D. Reciprocating pump
Answer» E.
97.

The discharge through a reaction turbine __________ with the increase in unit speed.

A. remains same
B. increases
C. decreases
D. None of these
Answer» D. None of these
98.

In an outward flow reaction turbine

A. the water flows parallel to the axis of the wheel
B. the water enters at the centre of the wheel and then flows towards the outer periphery of the wheel
C. the water enters the wheel at the outer periphery and then flows towards the centre of the wheel
D. the flow of water is partly radial and partly axial
Answer» C. the water enters the wheel at the outer periphery and then flows towards the centre of the wheel
99.

The gross or total head of the turbine is the __________ of the water levels at the head race and tail race.

A. sum
B. difference
C. product
D. None of these
Answer» C. product
100.

The speed of a turbine runner is

A. directly proportional to H^1/2
B. inversely proportional to H^1/2
C. directly proportional to H^3/2
D. inversely proportional to H^3/2
Answer» B. inversely proportional to H^1/2