Quiz: Mechanical Engineering 21 May 2020

Quiz: Mechanical Engineering
Exam: UPPSC AE
Topic: Miscellaneous

Each question carries 1 mark
Negative marking: 1/3 mark
Time: 10 Minutes

Q1. In offset slider crank mechanism, the ratio of the working stroke time to the return
stroke time is
(a) less than 1
(b) equal to 1
(c) more than 1
(d) no specific range or value

Q2. Match List-I with List-II and select the correct answer using the given lists:
List-I
A. Compound train
B. Quick return mechanism
C. Exact straight-line motion
D. Approximate straight-line motion
List-II
a. Hart mechanism
b. Coriolli’s force
c. Transmission of motion around bends and corners
d. Watt mechanism

(a) A – a, B – b, C – c, D – d
(b) A – c, B – b, C – a, D – d
(c) A – c, B – d, C – a, D – b
(d) A – a B – d, C – c, D- b

Q3. A system and its environment put together constitute
(a) an adiabatic system
(b) an isolated system
(c) a segregated system
(d) a homogenous system

Q4. For a system to be in thermodynamic equilibrium the system and its surroundings
are to be in
(a) Thermal equilibrium
(b) Chemical equilibrium
(c) Mechanical equilibrium
(d) Thermal, chemical and mechanical equilibrium

Q5. In a centrifugal compressor, an increase in speed at a given pressure ratio causes.
(a) increase in flow and increase in efficiency
(b) increase in flow and decrease in efficiency
(c) Decrease in flow and decrease in efficiency
(d) decrease in flow and increase in efficiency

Q6. Consider the following statements about true-stress-strain method:
1. It is more sensitive to changes in both metallurgical and mechanical conditions.
2. It gives a more accurate picture of the ductility.
3. It can be correlated with stress-strain values in other tests like torsion, impact,
combined stress tests etc.
4. It can be used for compression tests as well.
Which of the above statements are correct?
(a) 1,2 and 3
(b) 1,3 and 4
(c) 2,3 and 4
(d) All of the above

Q7. Detonation in the SI engine becomes severe during
(a) Low load and high speed
(b) High load and high speed
(c) Low load and low speed
(d) High load and low speed

Q8. The static friction
(a) bears a constant ratio to the normal reaction between the two surfaces
(b) is independent of the area of contact, between the two surfaces
(c) always acts in a direction, opposite to that in which the body tends to move
(d) all of the above

Q9. What happens to the specific volume of water when it is heated at 0°C?
(a) Decreases steadily
(b) Increases steadily
(c) first increases then decreases
(d) First decreases then increases

Q10. The Porter governor is an example of…………
(a) Inertia governor
(b) Flywheel governor
(c) Centrifugal governor
(d) None of these

SOLUTIONS
S1. Ans.(c)
Sol. A slider crank mechanism is a quick-return motion mechanism. In which return stroke
time is less than the forward stroke time

S2. Ans.(b)
Sol. Hart mechanism is an exact straight-line mechanism.
Quick return motion mechanism has one link (slider) translating on another rotating link. Which causes Coriolis acceleration in slider.

S3. Ans (b)
Sol. A system and its surrounding constitute a universe which is an isolated system.

S4. Ans (d)
Sol. A thermodynamic system will be in thermodynamic equilibrium with its surrounding when it is in thermal equilibrium (temperature is equal to surrounding), chemical equilibrium (chemical potential of system with respect to surrounding is zero) and mechanical equilibrium (Pressure of system is equal to that of surrounding) simultaneously.

S5. Ans.(b)
Sol. By increase in speed at a given pressure ratio, mass flow rate increases but-efficiency decreases due to various frictional losses.

S6. Ans (d)
Sol.
True stress-strain curve is more sensitive to changes in both metallurgical and mechanical conditions, it can give a more accurate picture of the ductility and can be correlated with stress-strain values in other tests like torsion, impact, combined stress tests etc.

S7. Ans (d)
Sol. Detonation in SI engine will become severe at high load and low speed because at higher loads, the temperature of cylinder and combustion chamber walls will be higher and hence temperature of the end charge will be more which increases knocking tendency in SI engine and at lower engine speed, longer will be the absolute time for the flame to traverse the cylinder which increases the time available for pre flame reactions hence the tendency to knock increases.

S8. Ans.(d)
Sol. In case of static friction it is the ratio of Normal reaction between the surface to the friction force.
It is always opposing the motion or tending to motion of the body so always act in opposite direction.

S9. Ans.(d)
Sol. As, density of water is maximum at 4°C so when temperature of water is increased then upto 4°C specific volume decreases due to density increase and after that specific volume increase.

S10. Ans.(c)
Sol. Types of centrifugal governor.
(1) Watt governor
(2) Porter governor
(3) Proell governor
(4) Hartnell governor
In centrifugal governor, centrifugal force on balls will decide the sleeve movement and control the mean speed.

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