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# Machine Dynamics MCQ – Sensitiveness and Stability of Governors

For a given fraction of change in speed, a more sensitive governor will have a ______

a) Higher lift

b) Lower lift

c) More effective length

d) Less effective length

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Answer: a

Explanation: For an independent governor, the greater the lift of the sleeve corresponding to a given fractional change in speed, the greater is the sensitiveness of the governor. Hence the sleeve lift is directly proportional to the fractional change in speed.

For a given lift of the sleeve, the sensitiveness of the governor increases as the speed range decreases

a) True

b) False

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Answer: a

Explanation: The greater the lift of the sleeve corresponding to a given fractional change in speed, the greater is the sensitiveness of the governor, this is for an independent governor. Hence the given statement is true.

The equilibrium speed of a governor varies from 30 rpm to 20 rpm, find the sensitiveness of the governor.

a) 0.4

b) 1.5

c) 0.66

d)1.25

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Answer: a

Explanation: Mean speed = (20+30)/2 = 25 rpm

Difference in max and min speed = 30-20 = 10 rpm

sensitiveness = 10/25 = 0.4.

When a governor is fitted into an engine, then sensitiveness is defined as the ratio of ________ of maximum and minimum speed to the mean speed.

a) Sum

b) Difference

c) Product

d) Root mean square

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Answer: b

Explanation: For an independent governor, steadiness can be defined in terms of sleeve lift and change in speed, but however when the governor is fitted into an engine then the sensitiveness is defined as the ratio of the difference between the maximum and minimum equilibrium speeds to the mean equilibrium speed.

Consider two governors A and B running at the same speed. When this speed increases or decreases by a certain amount, the lift of the sleeve of governor A is greater than the lift of the sleeve of governor B. Which of the following statement is true for the above situation?

a) Governor A is more sensitive than B

b) Governor B is more sensitive than A

c) Governor A is equally sensitive as B

d) Lift does not affect sensitivity

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Answer: a

Explanation: For an independent governor, the greater the lift of the sleeve for a given fractional change in speed, the greater will be the sensitiveness of the governor. As a consequence, we can establish a relation in which the sensitiveness of the governor is related to sleeve lift and fractional change in speed.

For a governor, the sensitivity is 0.5 and the mean speed is 20 rpm, find the maximum speed.

a) 15 rpm

b) 25 rpm

c) 30 rpm

d) 40 rpm

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Answer: b

Explanation: 20 = (N1+N2)/2 :: 40 = N1 + N2

0.5×20 = N1-N2

therefore N1 = 25 rpm.

For a governor, the sensitivity is 0.5 and the mean speed is 20 rpm, find the minimum speed.

a) 15 rpm

b) 25 rpm

c) 30 rpm

d) 40 rpm

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Answer: a

Explanation: 20 = (N1+N2)/2 :: 40 = N1 + N2

0.5×20 = N1-N2

10 = N1-N2

therefore N1= 25 rpm

N2 = 15 rpm.

For a stable governor, if the equilibrium speed increases, the radius of governor balls must also increase.

a) True

b) False

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Answer: a

Explanation: For a stable governor: the radius of governor balls increases with increase in equilibrium speed, a governor is said to be unstable if the radius of rotation decreases with increase in speed.

On which of the following factors, the stability of governor does not depend?

a) Speed

b) Radius of rotation

c) Governor equilibrium

d) Mass of the engine

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Answer: d

Explanation: For the stability of the governor, with the increase in the equilibrium speed, the radius of governor balls should also increase, a governor is said to be unstable if the radius of rotation decreases with increase in speed.

When the governor is too sensitive, then which of the following process occurs?

a) Hunting

b) More stability

c) Less variation in speed

d) Increased steadiness

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Answer: a

Explanation: Hunting is a process in which the speed of the engine is continuously fluctuating above and below the mean speed. This is something which happens when a governor is too sensitive.