The kinetic energy of a circular disc rotating with a speed of 60 r.p.m. about an axis passing through a point on its circumference and perpendicular to its plane is (mass of circular disc = 5 kg, radius of disc = 1m) approximately.

Options

A. 170 J
B. 160 J
C. 150 J
D. 140J

Answer

(c)

Explanation

Rotational `KE=(1)/(2)1omega^(2)`
`I=(MR^(2))/(2)+MR^(2)=(3)/(2)MR^(2)`
`R.K.E=(1)/(2)Iomega^(2)=(1)/(2)xx((3)/(2)MR^(2))xxomega^(2)`
`=(1)/(2)xx(3)/(2)xx(1)^(2)xx(2pi)^(2)=(3)/(4)xx5xx4pi^(2)`
`=15pi^(2)=150J`