If earth suddenly contracts to 0.5 times of its present radius, then the length of the day becomes

Options

A. 12 hr
B. 18 hr
C. 15.5 hr
D. 6 hr

Answer

d

Explanation

`I_(1) omega_(1) = I_(2) omega_(2)` (law of conservation of angular)
`((2)/(5)MR_(1)^(2))(2pi)/(T_(1)) = ((2)/(5)MR_(2)^(2))(2pi)/(T_(2)), 0.5R_(1) = R_(2)`
`T_(2) = ((0.5 R_(1))/(R_(1)))^(2) T_(1) = 6 hr" "(because T_(1) = 24 hr.)`