Engineering Questions with Answers - Multiple Choice Questions
Machine Dynamics MCQ – Turning Moment Diagram for a Multicylinder Engine
1 - Question
For a multicylinder engine, the moment of inertia of a flywheel is 6500 kg-m2, from the turning moment diagram, it is found that fluctuation of energy is 56000 N-m, if mean speed is 120 rpm, then find maximum speed.
a) 121
b) 119
c) 122
d) 118
View Answer
Answer: a
Explanation: We know that ΔE= I ω2. Cs
= I ω. (ω1-ω2)
= 6500. 120x(2π/60)2(N1-N2)
N1-N2 = 2
N=120
Therefore, N1=121.
2 - Question
Multi cylinder engines are usually placed at an equal inclination to each other.
a) True
b) False
View Answer
Answer: a
Explanation: In case of multi cylinder engines, the cylinders are placed in such a way that the performance of the engine is optimum hence placing them at equal inclination improves the performance.
3 - Question
Consider a three cylinder engine, the resultant turning moment diagram is the _____ of three cylinders.
a) Sum
b) Difference
c) Product
d) Independent
View Answer
Answer: a
Explanation: For a multicylinder engine, the turning moment diagram is formed by combining the turning moment diagrams of individual cylinders.
4 - Question
For a multicylinder engine, the coefficient of fluctuation of speed would vary with _________
a) Number of cylinders
b) Remains unaffected
c) Length of connecting rod
d) Input temperature
View Answer
Answer: b
Explanation: The coefficient of fluctuation depends only on the speed of the engine and is unaffected by the no. of cylinders.
5 - Question
For a 4 cylinder engine, if the minimum speed of the engine is half the maximum speed, then coefficient of fluctuation is _________
a) 0.5
b) 1.5
c) 2
d) 0.66
View Answer
Answer: d
Explanation: Let N be the maximum speed, then minimum speed is N/2
mean speed = (N+N/2)/2 = 3N/4
Maximum fluctuation = N – N/2 = N/2
therefore coefficient of fluctuation = 2/3.
6 - Question
In the turning moment diagram of a multicylinder engine, the work done during exhaust stroke is by ______
a) The gases
b) On the gases
c) Piston wall
d) Valve
View Answer
Answer: b
Explanation: During exhaust stroke, the area under the loop is negative. This indicates that the work is done on the gases and power has not been generated during the process.
7 - Question
For a 4 cylinder engine, when the pressure inside the cylinders exceeds the atmospheric pressure then.
a) Work is done by the gases
b) Work is done on the gases
c) Work is done on the piston wall
d) Work is done by the piston wall
View Answer
Answer: a
Explanation: When the pressure inside the cylinders exceeds the atmospheric pressure then the area under the loop is positive. This indicates that the work is done by the gases.
8 - Question
The flywheel of a steam engine has a mass moment of inertia of 2500 Kg-m2. The starting torque of the steam engine is 1500 N-m and may be assumed constant, using this data find the angular acceleration of the flywheel in rad/s2.
a) 0.4
b) 0.6
c) 0.3
d) 1.2
View Answer
Answer: a
Explanation: We know that T = I.α
T = 1500 Nm (constant )
I = 2500 kg-m2
therefore, &aplpha; = 15/25 = 0.6 rad/s2.