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# Machine Kinematics – Bifilar Suspension

1 - Question

Which of the following apparatus is used to find the moment of inertia of an object?

a) Simple pendulum

b) Bifilar suspension

c) Compound pendulum

d) Spring pendulum

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Answer: bExplanation: Experimentally, the moment of inertia of any rigid body can be calculated with an apparatus called bifilar suspension.

2 - Question

The strings used in bifilar suspension are perpendicular.

a) True

b) False

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Answer: bExplanation: The body whose moment of inertia is to be determined is suspended by two long parallel flexible strings.

3 - Question

From the following data calculate the radius of gyration of the connecting rod.

mass of connecting rod = 1.5 Kg, length of wires = 1.25m, distance of wires to the rods = 0.12m

Time for 20 oscillations = 40 secs.

a) 107 mm

b) 110 mm

c) 95 mm

d) 100 mm

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Answer: aExplanation: From the given data x=y= 0.12m T = 40/20 = 2 sec, f = 0.5sec Substituting the values into the bifilar expression we get Kg = 107 mm.

4 - Question

From the following data calculate the mass moment of inertia of the connecting rod in Kg-m2.

mass of connecting rod = 1.5 Kg, length of wires = 1.25m, distance of wires to the rods = 0.12m, Time for 20 oscillations = 40 secs.

a) 0.107

b) 0.017

c) 0.095

d) 0.010

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Answer: bExplanation: From the given data x=y= 0.12m T = 40/20 = 2 sec, f = 0.5sec Substituting the values into the bifilar expression we get k = 107 mm = 0.107m I = mk2 = 0.017 Kg-m2.

5 - Question

A rigid body has a radius of gyration of 20cm, if its moment of inertia is 10 Kg-m2, find its mass in kilograms.

a) 250

b) 225

c) 500

d) 125

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Answer: aExplanation: We know that I = mk2 Now I = 10 Kg-m2 and k = 0.2m therefore m = I/k2 = 10/0.04

6 - Question

In a bifilar suspension, if the length of the connecting rod is decreased, which of the following quantities will increase?

a) Time period

b) Frequency

c) Radius of gyration

d) Acceleration

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Answer: bExplanation: In a bifilar suspension, the frequency of vibration depends inversely on the square root of the length, hence decreasing length will result in increasing the frequency.

7 - Question

When the body is twisted through a small angle θ about a vertical axis through the centre of gravity, which of the following motion will occur?

a) Angular Simple Harmonic Motion

b) Linear Simple Harmonic Motion

c) Linear accelerated motion

d) Angular accelerated motion

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Answer: aExplanation: When a body is subjected to torsion then it twists by a small angle θ about a vertical axis through the centre of gravity which is generally denoted by G, it will vibrate with simple harmonic motion in a horizontal plane.

8 - Question

To determine moment of inertia of a rigid object both bifilar and trifilar suspensions can be used.

a) True

b) False

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Answer: aExplanation: The mass moment of inertia of any rigid object can be determined experimentally using an apparatus called bifilar suspension and trifilar suspension.