A uniform metre scale of mass 0.2 kg is rotated about an axis passing through its one end and perpendicular to its length, at the rate of 60 revolutions/minute. What is its kinetic energy of rotation? `("use "pi^(2)=10)`

Options

A. 3/4 J
B. 4/3 J
C. 2.5 J
D. 0.5 J

Answer

B

Explanation

The M.I. of the metre scale about an axis passing through its one end and perpendicular to its length is given by
`I=(mL^(2))/(3)=(0.2xx1^(2))/(3)=(1)/(15)" and n = 1 rev/s"`
`therefore" Its K.E."=(1)/(2)Iomega^(2)=(1)/(2)"I. "4pi^(2)n^(2)`
`=(1)/(2)xx(1)/(15)xx4xx10xx1=(4)/(3)J`