11

12

13

a)
b)

03000ME304052001

A machine supported symmetrically on four springs has a mass of 70kg. The mass of
the reciprocating part is 3kg which moves through a vertical stroke of 150mm with
simple harmonic motion. Determine the combined stiffness of the springs so that the
force transmitted to the foundation is 1/20" of the impressed force. Neglect damping.
If under actual working conditions, the damping reduces the amplitudes of successive
vibrations by 25%. Find (1) the force transmitted to the foundation at 1000rpm 2)
The force transmitted to the foundation at resonance

What is the whirling speed of a shaft? Explain

Calculate the whirling speed of a shaft 20 mm diameter and 0.6 m long carrying a
rotor of mass of 1 kg at its mid-point. The density of the shaft material is 7680 kg/m’,
and the modulus of elasticity is 200GN/m’. Assume the shaft is supported on short
bearings

A single cylinder IC Engine directly drives an electric generator. The rotating mass
of the engine, flywheel and rotor of generator with the shaft is equivalent to a three-
rotor system as shown in figure. The mass moment of inertia of rotors A, B and C are
0.15, 0.3 and 0.1kgm’. The modulus of rigidity of the shaft material is 8610/1173.
Calculate the natural frequency of torsional vibrations.

14 a) Explain torsionally equivalent shaft and derive an expression for it.
b) Write brief notes on vibration isolation

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