Quiz: Mechanical Engineering 14 July 2020

Quiz: Mechanical Engineering
Exam: ISRO (TECHNICAL ASST.)
Topic: Miscellaneous

Each question carries 4 mark.
Negative marking: 1 mark
Time: 15 Minute

Q1. The shape and size of sand grains affects which of the following properties?
(a) Adhesiveness
(b) Porosity
(c) Refractoriness
(d) Strength

Q2. The percentage of carbon that must be present in steel before it can be hardened noticeably:
(a) 0.05
(b) 0.1
(c) 0.2
(d) 0.3

Q3. A master gauge is mainly used for which of the following purpose?
(a) checking thread cutting angle
(b) measuring internal diameter
(c) verifying the accuracy of gauges used on shop floor
(d) None of these

Q4. According to which law, for all perfect gases there is a change in volume by (1/273)th of their original volume at 0 deg C for every 1 deg C change in temperature when pressure remains constant.
(a) Joule’s law
(b) Boyle’s law
(c) Regnautt’s law
(d) Charles’ law

Q5. Which equation best represents the entropy (s) of a system with two parts with entropy x and y respectively?
(a) s = x + y
(b) s = x – y
(c) s < x + y
(d) s > x + y

Q6. Diesel cycle consists of which four processes?
(a) two isothermal and two isentropic processes
(b) two isentropic and two constant volume processes
(c) two isentropic, one constant volume and one constant pressure processes
(d) two isentropic and two constant pressure processes

Q7. Which of the following boiler is suitable to meet fluctuating demands?
(a) Babcock and Wilcox
(b) Locomotive
(c) Lancashire
(d) Cochran

Q8. Resilience of a material is important, if it is subjected to ______.
(a) Combined loading
(b) Fatigue
(c) Thermal stresses
(d) Shock loading

Q9. A balloon lifting in air follows the _______
(a) Law of gravitation
(b) Archimedes principle
(c) Principle of buoyancy
(d) All options are correct

Q10. In a single casing, multi-stage pump running at constant speed, the capacity rating is to be slightly lowered. It can be done by
(a) designing the new impeller
(b) trimming the impeller size to the required size by machining
(c) no means
(d) some other alterations in the impeller

Solutions

S1. Ans (b)
Sol. The shape and size of sand grains determine the porosity of the sand mould. If fine grain sand is used then porosity is less due to little space between sand particles and if coarse grain sand is used then porosity is high because of enough space between sand particles.

S2. Ans (d)
Sol. Low carbon steel which has 0.15 to 0.25% of carbon cannot be hardened by heating and subsequent quenching due to low carbon percentage. So, percentage of carbon must be about 0.3 % to get the steel hardened.

S3. Ans (c)
Sol. Master gauge is a very accurate gauge used only as a standard of reference for working gauges.

S4. Ans (d)
Sol. According to Charles’ law, for all perfect gases there is a change in volume by (1/273)th of their original volume at 0 deg C for every 1 deg C change in temperature when pressure remains constant.

S5. Ans (d)
Sol. Assume the combined system as isolated system. As entropy of an isolated system always increases, so s > x + y

S6. Ans (c)
Sol. A diesel cycle consists of four processes mainly:
1. Isentropic compression
2. Constant pressure heat addition
3. Isentropic expansion
4. Constant volume heat rejection

S7. Ans (b)
Sol. Locomotive boiler is a horizontal drum axis, multi-tubular, natural circulation, natural draft, solid fuel, fixed fire tube boiler. It is used to meet fluctuating demands.

S8. Ans (d)
Sol. When a material component is subjected to shock loading then a property comes into picture that is called resilience. Resilience is defined as the strain energy absorbed by the material within the elastic limit.

S9. Ans (d)
Sol. A balloon lifting in air follows law of gravitation, law of buoyancy or Archimedes principle for defining its equilibrium.

S10. Ans (b)
Sol. In a single casing, multi-stage pump running at constant speed, the capacity rating can be lowered by trimming the impeller size to the required size by machining.

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