# Strength of Materials Questions and Answers – Composite Shaft

This set of Strength of Materials Multiple Choice Questions & Answers (MCQs) focuses on “Composite Shaft”.

1. Calculate that torque, if the diameter of the shaft is 50 mm and revolutions @ 130 rpm. The maximum shear stress is 62.5 N/mm2.
a) 1564 Nm
b) 1478 Nm
c) 1534 Nm
d) 1494 Nm

Explanation: Diameter of shaft = 50 mm
Revolutions of shaft = 130 rpm.
Maximum shear stress = f= 62.5 N/mm2.
T = f π D3/ 16
T = 62.5 ×503× π / 16.
T = 1534 Nm.

2. What is the example for a centrifugal pump?
a) Reciprocating pump
b) Suction pump
c) Rotodynamic pump
d) Delivery pump

Explanation: Rotodynamic pumps have a rotating element through which as the liquid passes its angular momentum changes, due to which the pressure energy of the liquid is increased. The centrifugal pump is a rotodynamic pump.

3. Reciprocating pump is an example of ___________
a) Positive displacement pump
b) Delivery pump
c) Suction pump
d) Rotodynamic pump

Explanation: Positive displacement pumps are those pumps in which the liquid is sucked and then it is pushed to the thrust exerted on it by a piston. The most common example of the positive displacement pump is the reciprocating pump.

4. ____ is the difference between theoretical discharge and the actual discharge of the pump.
a) Crank
b) Hook
c) Slip
d) Centile

Explanation: c
Explanation: Slip of a pump is defined as the difference between the theoretical discharge and actual discharge after pump.

5. _____ is a phenomenon by which the study and continuous flow of liquid are obstructed.
a) Slip
b) Separation
c) Air vessels
d) Knockage

Explanation: Separation of reciprocating pump is that phenomenon by which the steady and continuous flow of liquid is affected by the presence of air and dissolved gases.

6. Negative slip occurs when the______ is more than theoretical discharge.
a) Virtual discharge
b) Actual discharge
c) Mean discharge
d) Mode discharge

Explanation: When the delivery valve opens before the suction stroke is completed, the actual discharge is more than the theoretical discharge. In such cases, the slip of the pump is known as a negative slip.

7. _____ slip occurs, when the delivery pipe is short and the suction pipe is long.
a) Positive
b) Critical
c) Negative
d) Zero

Explanation: The slip occurs when the delivery pipe is short and the suction pipe is long. The pump is running at high speeds as the delivery valve open before a suction stroke is completed, the slip of the pump is known as negative slip.

8. ________ reduces the possibility of separation.
a) Air vessels
b) Casing
c) Impeller
d) Vortex

Explanation: An air vessel may be a closed chamber having the compressed air in a top portion and the water at the bottom. It reduces the possibility of separation and it ensures the pump to run at high speed.

9. If the absolute pressure falls below ___________ m, the pump prone to separation.
a) 3 m
b) 2 m
c) 1.5 m
d) 2.5 m

Explanation: If the absolute pressure falls below 2.5 metres of water, the dissolved gases will be appearing in a liquid and continuous flow will be chocked. This phenomenon can be termed as separation.

10. The phenomenon of separation can also be known as ___________
a) Cavitation
b) Priming
d) Pulsate

Explanation: Separation is a phenomenon of obstructing the flow by the presence of dissolved gases when the absolute pressure falls below 2.5 metres of water. This phenomenon of separation can also be known as knocking (or) cavitation in the reciprocating pump.

11. The work done against friction is reduced due to _____________
a) Impeller
b) Priming
c) Air vessel
d) Vortex

Explanation: An air vessel is fitted to the suction and delivery pipes at a point close to the cylinder of a single acting reciprocating. The pump increases the length of the suction pipe and reduces the work done against friction.

12. Volute is a type of _____________
a) Delivery pipe
b) Casing
c) Impeller
d) Suction pipe

Explanation: Casing is an airtight chamber covering the impeller. The different types of casing
i.Volute casing
ii.Vortex casing
iii.Casing with guide blades.

13. ______ pumps, the torque is uniform.
a) Reciprocating pump
b) Suction pump
c) Delivery pump
d) Centrifugal pump

Explanation: Centrifugal pump is used for lifting highly viscous liquids such as oils, muddy and sewage water, paper pulp etc. In centrifugal pump, torque is uniform and no air vessels are required.

14. What is the practical maximum suction lift in a reciprocating pump?
a) 3.5 m
b) 4.5 m
c) 5 m
d) 6.5 m

Explanation: Reciprocating pump can handle only pure water or less viscous liquids free from impurities. It can be operated at low speeds only. The practical maximum section lift is 6.5 metres.

15. _____ pumps give a larger discharge.
a) Suction
b) Reciprocating
c) Centrifugal
d) Positive displacement

Explanation: Centrifugal pump are an example of rotodynamic pump the basic principle of centrifugal pump is that “when a certain mass of liquid is rotated by an external force, then the centrifugal head is impressed which enables it to rise to a higher level”. A centrifugal pump discharges a larger quantity when compared to other pumps.

Sanfoundry Global Education & Learning Series – Strength of Materials.

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