System of Particles and Rotational Motion - Result Question 68

75. The moment of inertia of a body about a given axis is 1.2kgm2. Initially, the body is at rest. In order to produce a rotational kinetic energy of 1500 joule, an angular acceleration of 25radian/sec2 must be applied about that axis for a duration of

[1990]

(a) 4 seconds

(b) 2 seconds

(c) 8 seconds

(d) 10 seconds

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Answer:

Correct Answer: 75. (b)

Solution:

  1. (b) I=1.2kgm2,Er=1500J, α=25rad/sec2,ω1=0,t= ? As Er=12Iω2,ω=2ErI

=2×15001.2=50rad/sec

From ω2=ω1+αt

50=0+25t,t=2 seconds 



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