⚙️ Mechanical Eng Solved MCQs with Answers

Practice 934 approved ⚙️ Mechanical Eng questions with verified answers from the 🛠️ Engineering Essentials subject for Pakistan exams.

934 solved MCQs

The Bernoulli's equation is based on the assumption thatAnswer: All of the above Power required to drive a centrifugal pump is directly proportional to __________ of its impeller.Answer: fourth power of diameter The mechanical efficiency of an impulse turbine isAnswer: ratio of the actual work available at the turbine to the energy imparted to the wheel The overshot water wheels are those in which the wheel runs entirely by the __________ of water.Answer: weight In a Kaplan turbine runner, the number of blades are generally betweenAnswer: 4 to 8 If Hg is the gross or total head and hᶠ is the head lost due to friction, then net or effective head (H) is given byAnswer: H = Hᵍ - hᶠ Discharge of a centrifugal pump isAnswer: directly proportional to (diameter)² of its impeller 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 power of the wheel isAnswer: 1.75 kW The static head of a centrifugal pump is equal to the __________ of suction head and delivery head.Answer: sum The ratio of actual work available at the turbine to the energy imparted to the wheel is known as __________ efficiency.Answer: mechanical Geometric similarity is said to exist between the model and the prototype, if both of themAnswer: are identical in shape, but differ only in size The speed of a turbine runner isAnswer: directly proportional to H¹ᐟ² Discharge of a centrifugal pump is (where N = Speed of the pump impeller)Answer: directly proportional to N In a reaction turbine, the draft tube is usedAnswer: to increase the head of water by an amount equal to the height of the runner outlet above the tail race The power produced by the reaction turbine is __________ to the head of water.Answer: directly proportional Slip of a reciprocating pump is defined as theAnswer: difference of theoretical discharge and the actual discharge The efficiency of a centrifugal pump will be maximum when the blades are bent backward.Answer: Yes Multi-stage centrifugal pumps are used toAnswer: produce high heads The specific speed of a centrifugal pump, delivering 750 litres of water per second against a head of 15 metres at 725 r.p.m., isAnswer: 82.4 r.p.m. Theoretical power required (in watts) to drive a reciprocating pump is (where w = Specific weight of liquid to be pumped in N/m³, Q = Discharge of the pump in m³/s, Hₛ = Suction head in metres, and Hᵈ = Delivery head in metres)Answer: wQ(Hₛ + Hᵈ) Which of the following pump is preferred for flood control and irrigation applications?Answer: Axial flow pump The efficiency of a Pelton wheel working under constant head __________ with the increase in power.Answer: increases The discharge of a centrifugal pump working under constant head __________ with the speed.Answer: increases Delivery head of water of a centrifugal pump is inversely proportional to diameter of its impeller.Answer: No Which of the following turbine is preferred for 0 to 25 m head of water?Answer: Kaplan turbine The speed ratio of a Francis turbine is defined as the ratio of the theoretical jet velocity to the peripheral speed at inlet.Answer: No The overall efficiency of a reaction turbine is the ratio ofAnswer: power produced by the turbine to the energy actually supplied by the turbine Work done by a turbine __________ upon the weight of water flowing per second.Answer: depends The maximum number of jets, generally, employed in an impulse turbine without jet interference areAnswer: six Discharge (Q) of a centrifugal pump is given by (where D = Diameter of impeller at inlet, b = Width of impeller at inlet, and Vᶠ = Velocity of flow at inlet)Answer: Q = π.D.b.Vᶠ