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# Machine Dynamics MCQ – Swaying Couple

The unbalanced forces along the line of stroke for the two cylinders constitute a ______ about the centre line between the cylinders.

a) Tension

b) Compression

c) Torsion

d) Couple

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Answer: d

Explanation: The unbalanced forces along the line of stroke for the two cylinders constitute a couple about the centre line between the cylinders. This couple is known as swaying couple as it has a swaying effect.

This couple has swaying effect about a horizontal axis.

a) True

b) False

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Answer: b

Explanation: This couple has swaying effect about a vertical axis, and tends to sway the engine alternately in clockwise and anticlockwise directions. About horizontal axis no swaying effect is observed.

Which of the following has a tendency to sway engine in alternately in clockwise and anticlockwise directions?

a) Swaying couple

b) Tractive force

c) Hammer blow

d) Hammer couple

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Answer: a

Explanation: A couple having a swaying effect about a vertical axis, and a tendency to sway the engine alternately in clockwise and anticlockwise directions is known as swaying couple.

At which of the following angles in degrees does the swaying couple attains a maximum value?

a) 135

b) 45

c) 90

d) 60

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Answer: b

Explanation: The swaying couple is maximum or minimum when (cosθ + sin θ) is maximum or minimum. This results in a relation tanθ=1

hence theta = 45 degrees or 225 degrees.

If the maximum value occurs at 45 degrees then at which of the following angles in degrees will the swaying couple attains its maximum value again?

a) 135

b) 45

c) 225

d) 60

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Answer: c

Explanation: The swaying couple is maximum or minimum when the relation (cos θ + sin θ) is maximum or minimum. This results in a relation tan θ=1

hence theta = 45 degrees or 225 degrees.

Find the maximum value of swaying couple in newtons from the following data:

m = 100Kg

ω = 300 rpm

radius = 0.6m

c = 2/3

a = 22–√m

a) 6978

b) 7574

c) 6568

d) 7374

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Answer: a

Explanation: The maximum value of Swaying couple is given by

+a/2–√ (1-c)mω^{2}r

substituting the values we get

F = 6978 N.

Find the minimum value of swaying couple in newtons from the following data:

m = 100Kg

ω = 300 rpm

radius = 0.6m

c = 2/3

a = 22–√m

a) -6978

b) -7574

c) -6568

d)- 7374

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Answer: a

Explanation: The minimum value of Swaying couple is given by

-(a/2–√)(1-c)mω^{2}r

substituting the values we get

F = -6978 N.

Swaying couple attains a maxima or minima when the crank angle is 45 degrees.

a) True

b) False

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Answer: a

Explanation: The swaying couple is maximum or minimum when the expression (cos θ +sin θ ) is maximum or minimum, differentiating it with respect to theta gives tan θ = 1

hence maximum/minimum value occurs at 45 or 225 degrees.

Find the variation in swaying couple in newtons from the following data:

m = 100Kg

ω = 300 rpm

radius = 0.6m

c = 2/3

a = 22–√m

a) 13956

b) 17574

c) 16568

d) 17374

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Answer: a

Explanation: The variation in tractive force is given by

±a/2–√ (1-c)mω^{2}r

substituting the values we get

F = 13956 N.

Find the maximum value of swaying couple in newtons from the following data:

m = 200Kg

ω = 300 rpm

radius = 0.6m

c = 2/3

a = 22–√m

a) 13956

b) 17574

c) 16568

d) 17374

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View Answer**

Answer: a

Explanation: The maximum value of Swaying couple is given by

+a/2–√(1-c)mω^{2}r

substituting the values we get

F = 13956 N.