If the earth were to contract such that its radius becomes one quarter. Without change in its mass, the duration of one full day would be

Options

A. A)3 h
B. B)1.5 h
C. C)6 h
D. D)4 h

Answer

B

Explanation

As angular momentum is conserved, so
`Iomega` = constant
`therefore I_(2)omega_(2)=I_(1)omega_(1)`
or `(2)/(5)M((R)/(4))^(2)xx(2pi)/(T)=(2)/(5)MR^(2)=(2pi)/(24)`
or `16T=24`
`implies T=1.5h`