Quiz: Mechanical Engineering 03 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 main advantage of shell moulding is that:
(a) a metallic pattern is used
(b) the moulds are stronger
(c) thin sections can be easily obtained
(d) high production rate is possible

Q2. Boring can be performed by
(a) boring machines only
(b) boring machines and lathe
(c) a machine only by single point high speed carbide tools
(d) boring machine, lathe and milling machine

Q3. Three states of matter are distinguished with respect to molecules by the
(a) Atoms in molecules
(b) Number
(c) Orientation
(d) Character of motion

Q4. The flow through a turbine in Mollier diagram is represented by a
(a) curved line convex up
(b) curved line convex down
(c) horizontal line
(d) vertical line

Q5. For the same output, same speed and same compression ratio, the thermal efficiency of a two-stroke cycle petrol engine as compared to that for four-stroke petrol engine is:
(a) Same as long as output is same
(b) More
(c) Same as long as compression ratio is same
(d) Less

Q6. The solid fuel having the highest calorific value is
(a) wood
(b) lignite
(c) coke
(d) anthracite

Q7. Which of the following is correct for validation of Hook’s law in simple tension test?
(a) Ultimate stress
(b) Breaking point
(c) Elastic limit
(d) Limit of proportionality

Q8. The mechanism obtained by fixing the sliding pair in single slider crank mechanism is:
(a) Bull engine
(b) Oscillating cylinder engine
(c) Gnome engine
(d) Crank and slotted lever quick return mechanism

Q9. A body is vibrating at 10 vibrations/second in simple harmonic motion of 10 cm amplitude. Th maximum velocity in cm/sec can be
(a) 100π
(b) 50 π
(c) 200 π
(d) 100 π

Q10. In an isothermal atmosphere, the pressure
(a) decreases linearly with elevation
(b) remains constant
(c) varies in the same way as the density
(d) increases exponentially with elevation

Solutions

S1. Ans (d)
Sol. The main advantages of shell moulding casting:
1.Good surface quality
2.High dimensional accuracy
3.Thin wall thickness and complex casting can be made
4.Less manpower and molding are required
5.High production rate

S2. Ans (d)
Sol. Boring is the process of enlarging a hole that has already been drilled (or cast) by means of a single-point cutting tool. It can be done by using boring machine, lathe and milling machine. Good surface finish is obtained in boring machine and lathe machine but not by milling machine due to intermittent cuts.

S3. Ans (d)
Sol. The states of matter are characterized by the motion of molecules in matter. There are three main states of matter i.e. solid, liquid and gas.

S4. Ans (d)
Sol. On Mollier diagram, the flow through a turbine is represented by a vertical line.

S5. Ans (d)
Sol. As losses of fuel in exhaust is high. So, for the same output, same speed and same compression ratio, the thermal efficiency of a two-stroke cycle petrol engine as compared to that for four-stroke petrol engine is less.

S6. Ans (d)
Sol. Anthracite is high rank coal used for industrial and residential applications. It has generally less than 10% volatile matter and a high carbon content (about 90% fixed carbon). Its gross calorific value is equal to or greater than 24 000 kJ/kg on an ash-free but moist basis.

S7. Ans (d)
Sol. Hook’s law is valid up to proportional limit. It states that the strain in a solid is proportional to the applied stress within the elastic limit or up to limit of proportionality of that solid.

S8. Ans (a)
Sol. Bull engine is the fourth inversion of single slider crank mechanism which is obtained when the slider is fixed.

S9. Ans (c)
Sol.
Given,
Amplitude (A) = 10 cm
Vibration speed (N) = 10 vibration/sec
Maximum velocity (Vmax)=A×2πN/60
=10×2π×10=200π

S10. Ans (a)
Sol. In an isothermal atmosphere, the pressure decreases exponentially upward.

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