Quiz: Mechanical Engineering 22 May 2020

Quiz: Mechanical Engineering
Exam: NLC GET
Topic: Miscellaneous
Each question carries 1 mark
Negative marking: 1/3 mark
Time: 10 Minutes

Q1. The maximum force which acts on the connecting rod is
(a) Force due to gas pressure
(b) Force due to inertia of piston
(c) Force due to friction of connecting rod
(d) Force due to crank pin

Q2. Strain rosettes are generally used for
(a) measurement of load
(b) measurement of shear strain
(c) measurement of longitudinal strain
(d) measurement of resilience

Q3. Toggle mechanism have following applications except
(a) Stone crushers
(b) Gear cutting
(c) Embossing presses
(d) Switches

Q4. Match the following List-I and List-II and select the correct answer using the codes
given below the lists:
List-I
A. Pantograph
B. Single slider crank chain
C. Double slider crank chain
D. Straight line motion
List-II
1. Scotch yoke mechanism
2. Double lever mechanism
3. Tchebicheff mechanism
4. Double crank mechanism
5. Hand pump
Codes:
A B C D
(a) 4 3 5 1
(b) 2 5 1 3
(c) 2 1 5 3
(d) 4 5 2 1

Q5. The delay period in CI engine depends upon
1. Temperature and pressure in the cylinder at the time of injection
2. Strength of fuel mixture
3. Relative velocity between the fuel injection and air turbulence pressure of residual gas
4. Engine output
Select the correct answer:
(a) 1, 2, 3 and 4
(b) 1, 2 and 3
(c) 1, 2 and 4
(d) 1, 3 and 4

Q6. At breakeven point:
(a) Sales revenue > total cost
(b) Sales revenue = total cost
(c) Sales revenue < total cost
(d) None of the above

Q7. In which of the following process, a small-diameter thick ring is expanded into a large diameter thinner ring by placing the ring between two rolls
(a) Shape rolling
(b) Tube rolling
(c) Ring rolling
(d) Continuous rolling

Q8. The instrument preferred in the measurement of highly fluctuating velocities in air flows is
(a) Pitot-static tube
(b) Propeller type anemometer
(c) Three cup anemometer
(d) Hot wire anemometer

Q9. A metal block is thrown into deep lake. As it sinks deeper in water, the buoyant force acting on it
(a) increases
(b) remains the same
(c) decreases
(d) first increases and then decreases

Q10. Match the following List-I with List-II and select the correct answer using the codes given below
List-I
A. Rigid coupling
B. Oldham’s coupling
C. Universal joint
D. Gear coupling
List-II
1. Permits greater torque capacity for a given size
2. Permits substantial angular misalignment of intersecting axes
3. Permits substantial lateral offset and little angular alignment
4. Permits almost no misalignment
Codes:
A B C D
(a) 1 2 3 4
(b) 4 2 3 1
(c) 1 3 2 4
(d) 4 3 2 1

 

SOLUTIONS

S1. Ans (a)
Sol. All of the given forces act on the connecting rod but the major force that acts on the connecting rod is the force due to gas pressure.

S2. Ans(c)
Sol. strain rosettes are generally used for measurement of longitudinal strain.
A strain gauge rosette is a term for an arrangement of two or more strain gauges that are positioned closely to measure strains along different directions of the component under evaluation. Single strain gauges can only measure strain effectively in one direction, so the use of multiple strain gauges enables more measurements to be taken, providing a more precise evaluation of strain on the surface being measured.

S3. Ans (b)
Sol. Stone crushers, embossing presses and switches works on toggle mechanism. Mechanical advantage of toggle mechanism is infinite or very large.

S4. Ans (b)
Sol. Pantograph utilizes double lever mechanism, Hand pump utilizes single slider crank chain, Scotch-yoke mechanism is an inversion of double slider crank chain and Tchebicheff mechanism is an approximate straight-line motion mechanism.

S5. Ans (a)
Sol. Following factors affects the delay period in CI engine
1. Temperature and pressure in cylinder
2. Engine output
3. Relative velocity of fuel injection and air turbulence
4. Strength of fuel mixture
5. Compression ratio

S6. Ans(b)
Sol. Breakeven point- The breakeven point is the level of production at which the costs of production equal the revenues for a product. At breakeven point, profit will be zero even there is no loss.
Which means sales revenue is equal to total cost.
Sales revenue = total cost

S7. Ans.(c)
Sol. Ring rolling is an operation of metal forming in which a small diameter, thick ring is
converted into large diameter, thinner ring by placing the ring between two rolls.

S8. Ans (d)
Sol. Hot wire anemometer is used for the measurement of highly fluctuating velocities in air. This can be done by measuring the heat loss of the wire which is placed in the fluid stream. The wire is heated by electrical current. The hot wire when placed in the stream of the fluid, in that case, the heat is transferred from wire to fluid, and hence the temperature of wire reduces. The resistance of wire measures the flow rate of the fluid which is the function of heat loss from the wire and change in the resistance of wire.

S9. Ans (b)
Sol. As buoyant force depends only on the displaced volume of fluid by the submerged or floating body according to Archimedes principle. So, volume displaced by the metal block will remain constant from when it sinks in the fluid till it sinks deeper, hence, the buoyant force on the metal block remains same.

S10. Ans (d)
Sol.
• Rigid coupling permits almost no misalignment.
• Oldham’s coupling permits substantial lateral offset and little angular alignment.
• Universal joint permits substantial angular misalignment of intersecting axes.
• Gear coupling permits greater torque capacity for a given size.

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.