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# Machine Dynamics MCQ – Controlling Force Diagram for a Porter Governor

The graph plotted between the controlling force of the governor and Radius of rotation is known as _______

a) Controlling force diagram

b) Radius of rotation diagram

c) Governor diagram

d) Sensitivity diagram

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Answer: a

Explanation: When the graph between the controlling force (FC) as ordinate and radius of rotation of the balls (r) as abscissa is drawn, then the graph obtained is known as controlling force diagram of the governor.

Controlling force is provided by spring and weight in the porter governor.

a) True

b) False

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Answer: b

Explanation: Controlling force is provided by the weight of the sleeve and ball in the porter governor and by the spring and the weight in Hartnell governor.

In the given figure, the x – axis represents radius of rotation and the y axis represents the controlling force. This graph is known as _________

a) Controlling force diagram of Porter governor

b) Controlling force diagram of Hartnell governor

c) Controlling force diagram of isochronous governor

d) Controlling force diagram of a general governor

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Answer: a

Explanation: The given figure is a plot between the controlling force and the radius of rotation, from the curve it is factually known that it represents the controlling force diagram of a porter governor.

What should be the stability condition for the angle made by OA and the x axis? (the x – axis represents radius of rotation and the y axis represents the controlling force.)

a) Angle must increase

b) Angle must decrease

c) Angle must remain constant

d) Stability is independent of this angle

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Answer: a

Explanation: In case the governor satisfies the condition for stability, the angle between OA and the x-axis must increase with the radius of rotation of the governor balls.

How should the equilibrium speed vary with the increase of radius of rotation of the governor balls for stability?

a) Must increase

b) Must decrease

c) Must remain constant

d) Equilibrium speed independent of radius of rotation

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Answer: a

Explanation: In order to achieve stability in a porter governor, the equilibrium speed must increase with the increase of radius of rotation of the governor balls.

For a more sensitive governor, the change in angle between OA and the x axis with change in radius of rotation should be? (the x – axis represents radius of rotation and the y axis represents the controlling force.)

a) Small

b) Large

c) Remain same

d) Is independent of this angle

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Answer: a

Explanation: For the governor to be more sensitive, the change in the value of angle between OA and the x-axis over the change of radius of rotation should be as small as possible.

In the given figure, the straight line OA represents _________ (the x – axis represents radius of rotation and the y axis represents the controlling force.)

a) Isochronous governor

b) Hartnell governor

c) Non – Isochronous governor

d) Stable governor

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Answer: a

Explanation: For the isochronous governor, the controlling force curve is a straight line passing through the origin, thus in the above figure, AO is passing through the origin.

In the given figure if the angle between OA and x-axis is made 90 degrees, the rotation speed will become 0. (the x – axis represents radius of rotation and the y axis represents the controlling force.)

a) True

b) False

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Answer: b

Explanation: In the given figure if the angle between OA and x-axis is made 90 degrees, the rotation speed will become infinite, as the speed is directly proportional to the root of tangent of that angle.