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in Machine Kinematics by (38.0k points)
In order to find the radius of gyration of a car, it is suspended with its axis vertical from three parallel wires 2.5 metres long. The wires are attached to the rim at points spaced 120° apart and at equal distances 250 mm from the axis. It is found that the wheel makes 50 torsional oscillations of small amplitude about its axis in 170 seconds. Find the radius of gyration of the wheel.

(a) 168 mm

(b) 268 mm

(c) 368 mm

(d) 468 mm

I have been asked this question during an online exam.

I would like to ask this question from Closely-coiled Helical Spring and Compound Pendulum topic in chapter Simple Harmonic Motion of Machine Kinematics

1 Answer

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by (106k points)
Correct option is (b) 268 mm

Explanation: Given : l = 2.5 m ; r = 250 mm = 0.25 m ;

Since the wheel makes 50 torsional oscillations in 170 seconds, therefore frequency of oscillation,

n = 50/170 = 5/17 Hz

Let kG = Radius of gyration of the wheel

We know that frequency of oscillation (n),

5/17 = r/2πkG √g/l  = 0.25/2πkG√9.81/2.5 = 0.079/kG

kG = 0.079 x 17/5 = 0.268 m = 268 mm.

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