Machine Dynamics Questions and Answers – Turning Moment Diagram for a Four Stroke Cycle Internal Combustion Engine

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This set of Machine Dynamics test focuses on “Turning Moment Diagram for a Four Stroke Cycle Internal Combustion Engine”.

1. Which of the following process is not the part of working of a 4 stroke I.C Engine?
a) Compression
b) Suction
c) Exhaust
d) Turbine flow
View Answer

Answer: d
Explanation: 4 stroke IC engine works through suction compression working or power stroke and then exhaust. It does not use turbine hence no turbine flow is used.
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2. 4-stroke engine has one power stroke per 2 revolutions hence turning moment diagram is uniform.
a) True
b) False
View Answer

Answer: b
Explanation: One power stroke per 2 revolutions of crank shaft hence its turning moment is not uniform so heavier flywheel is needed.

3. Work produced by the 4-stroke engine is less because _______
a) One power stroke per 2 revolutions
b) One power stroke per revolution
c) One power stroke per 4 revolution
d) Four power stroke per revolution
View Answer

Answer: a
Explanation: One power stroke per 2 revolutions of crank shaft hence its turning moment is not uniform so heavier flywheel is needed and hence results in less power generation.
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4. A negative loop is formed in the turning moment diagram because the pressure inside the cylinder is _______ than the atmospheric pressure.
a) Equal
b) More
c) Less
d) No pressure inside
View Answer

Answer: c
Explanation: A negative loop is formed in the turning moment diagram of a 4 stroke IC engine because during suction the pressure inside the engine is reduced due to intake and has a lower value than the atmospheric pressure.

5. When the work is done on the gases, which of the following effect is observed on the turning moment diagram?
a) Formation of negative loop
b) Formation of positive loop
c) Formation of an infinite loop
d) Formation of no loop
View Answer

Answer: a
Explanation: When the work is done on the gases, the pressure inside the cylinder decreases and has a value lower than the atmospheric pressure, as a result a negative loop is formed.
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6. When the work is by on the gases, which of the following effect is observed on the turning moment diagram?
a) Formation of negative loop
b) Formation of positive loop
c) Formation of an infinite loop
d) Formation of no loop
View Answer

Answer: b
Explanation: When the work is done by the gases, the pressure inside the cylinder increases and has a value higher than the atmospheric pressure, as a result a positive loop is formed.

7. Compression stroke results in ________
a) Formation of negative loop
b) Formation of positive loop
c) Formation of an infinite loop
d) Formation of no loop
View Answer

Answer: a
Explanation: During compression stroke, the work is done on the gases, the pressure inside the cylinder decreases and has a value lower than the atmospheric pressure, as a result a negative loop is formed.
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8. 4 strokes engine have a lower thermal efficiency than 2 stroke engine.
a) True
b) False
View Answer

Answer: b
Explanation: 4-stroke IC engines despite having low power output per cycle have a higher thermal efficiency than a 2 stroke cycle because in 2 stroke engines, the fuel escapes with the exhaust.

9. While drawing the turning moment diagram, which of the forces in not taken into account?
a) Inertia force
b) Force on connecting rod
c) Force on crank
d) Coriolis force
View Answer

Answer: d
Explanation: When a turning moment diagram is drawn, it takes into account all the forces inertia, connecting rod and crank however there is no coriolis force acting in the engine thus it is not taken into account.
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10. In the given turning moment diagram, the process X is known as ______
machine-dynamics-questions-answers-test-q10
a) Suction
b) Compression
c) Power
d) Exhaust
View Answer

Answer: c
Explanation: Since the area of the loop is maximum during the process X hence it is the power stroke since most the power is generated in this process which makes the pressure rise and create a positive loop.

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