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# Machine Dynamics MCQ – Hartnell Governor

Power of a governor is the

a) mean force exerted at the sleeve for a given percentage change of speed

b) workdone at the sleeve for maximum equilibrium speed

c) mean force exerted at the sleeve for maximum equilibrium speed

d) none of the mentioned

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Answer: d

Explanation: The power of a governor is the work done at the sleeve for a given percentage change of speed. It is the product of the mean value of the effort and the distance through which the sleeve moves. Mathematically,

Power = Mean effort × lift of sleeve

The effort of a Porter governor is equal to

a) c(m – M)g

b) c(m + M)g

c) C/(m + M)g

d c/(m – M)g

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Answer: b

Explanation: The effort of a Porter governor is equal to c(m + M)g.

The power of a Porter governor is equal to 4c^{2}/1 + 2c (m + M)gh.

The power of a Porter governor is equal to

a) c^{2}/1 + 2c (m + M)gh

b) 2c^{2}/1 + 2c (m + M)gh

c) 3c^{2}/1 + 2c (m + M)gh

d) 4c^{2}/1 + 2c (m + M)gh

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Answer: d

Explanation: The effort of a Porter governor is equal to c(m + M)g.

The power of a Porter governor is equal to 4c^{2}/1 + 2c (m + M)gh.

For the isochronous Porter governor, the controlling force curve is a straight line passing through the origin.

a) True

b) False

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Answer: a

Explanation: For the isochronous governor, the controlling force curve is a straight line passing through the origin. The angle φ will be constant for all values of the radius of rotation of the governor.

The controlling force diagram for a spring controlled governor is a curve passing through the origin.

a) True

b) False

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Answer: b

Explanation: The controlling force diagram for the spring controlled governors is a straight line.

A spring controlled governor is said to be unstable when the controlling force

a) increases as the radius of rotation decreases

b) increases as the radius of rotation increases

c) decreases as the radius of rotation decreases

d) remains constant for all radii of rotation

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Answer: c

Explanation: If the equilibrium speed of the governor decreases with an increase of the radius of rotation of balls, then the governor is said to be unstable.

In a spring controlled governor, when the controlling force _____________ as the radius of rotation increases, it is said to be a stable governor.

a) remains constant

b) decreases

c) increases

d) none of the mentioned

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Answer: c

Explanation: For the governor to be stable, in spring controlled governor, the controlling force must increase as the radius of rotation increases.

A spring controlled governor is said to be isochronous when the controlling force remains constant for all radii of rotation.

A spring controlled governor is said to be isochronous when the controlling force

a) increases as the radius of rotation decreases

b) increases as the radius of rotation increases

c) decreases as the radius of rotation decreases

d) remains constant for all radii of rotation

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Answer: d

Explanation: For the governor to be stable, in spring controlled governor, the controlling force must increase as the radius of rotation increases.

A spring controlled governor is said to be isochronous when the controlling force remains constant for all radii of rotation.

A spring controlled governor is found unstable. It can be made stable by

a) increasing the spring stiffness

b) decreasing the spring stiffness

c) increasing the ball mass

d) decreasing the ball mass

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Answer: b

Explanation: For the governor to be stable, in spring controlled governor, the controlling force must increase as the radius of rotation increases.

A spring controlled governor is said to be stable if the controlling force line when produced intersects the Y-axis

a) at the origin

b) below the origin

c) above the origin

d) any of the mentioned

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Answer: b

Explanation: A spring controlled governor is said to be stable if the controlling force line when produced intersects the Y-axis below the origin.

If the controlling force line for a spring controlled governor when produced intersects the Y-axis at the origin, then the governor is said to be isochronous.