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# Machine Dynamics MCQ– Hartung Governor

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

a) stable

b) unstable

c) isochronous

d) none of the mentioned

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Answer: c

Explanation: 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.

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 unstable.

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 unstable.

a) True

b) False

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Answer: a

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 unstable.

The relation between the controlling force (F_{c}) and radius of rotation (r) for a stable spring controlled governor is

a) F_{c} = ar + b

b) F_{c} = ar – b

c) F_{c} = ar

d) F_{c} = a/r + b

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Answer: b

Explanation: The relation between the controlling force (F_{C}) and the radius of rotation (r) for the stability of spring controlled governors is given by the following equation

F_{C} = a.r – b

A spring controlled governor is said to be unstable, if the relation between the controlling force (F_{c}) and radius of rotation(r) is F_{c} = ar

a) True

b) False

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Answer: b

Explanation: A governor is said to be unstable and the relation between the controlling force and the radius of

rotation is, therefore

F_{C} = a.r + b

When the relation between the controlling force (F_{c}) and radius of rotation (r) for a spring controlled governor is F_{c} = ar + b, then the governor will be

a) stable

b) unstable

c) isochronous

d) none of the mentioned

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Answer: b

Explanation: A governor is said to be unstable and the relation between the controlling force and the radius of

rotation is, therefore

F_{C} = a.r + b

A Hartnell governor has its controlling force (F_{c}) given by F_{c} = ar + b, where r is the radius of rotation and a and b are constants. The governor becomes isochronous when

a) a is + ve and b = 0

b) a = 0 and b is +ve

c) a is +ve and b is -ve

d) a is +ve and b is also +ve

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Answer: a

Explanation: None

Calculate the vertical height of a Watt governor when it rotates at 60 r.p.m.

a) 0.248 m

b) 0.248 m

c) 0.448 m

d) 0.548 m

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Answer: a

Explanation: Given : N_{1} = 60 r.p.m. ; N_{2} = 61 r.p.m.

Initial height

We know that initial height,

h_{1} = 895/(N_{1})^{2}

= 895/60^{2} = 0.248 m

The power of a governor is the work done at

a) the governor balls for change of speed

b) the sleeve for zero change of speed

c) the sleeve for a given rate of change of change

d) each governor ball for given percentage change of speed

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Answer: c

Explanation: Power of Governor: The work done by the governor on the sleeve to its equilibrium position for the fractional change in speed of governor is known as power of governor.

It is actually a work done. Power = Main force × Sleeve movement.

In a governor, if the equilibrium speed is constant for all radii of rotation of balls, the governor is said to be

a) Stable

b) unstable

c) inertial

d) isochronous

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Answer: d

Explanation: The governor is said to be Isochronous if the equilibrium speed is constant for all radii of rotation of balls.

A governor is said to be isochronous when the equilibrium speed is

a) variable for different radii of rotation of governor balls

b) constant for all radii of rotation of the balls within the working range

c) constant for particular radii of rotation of governor balls

d) constant for only one radius of rotation of governor balls

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Answer: b

Explanation: Isochronism in governor means constant equilibrium speed for all the radii of rotation.