If earth contract to half of its radius,what would be the duration of day?

The time will be 6 hours... As by conservation of angular momentum...we can easily get the final angular velocity of earth which will be 4 times the earlier one so the time period is Inversely proportional to angular velocity therefore it will decrease by 4 times

The moment of inertia (If I = 2/5 MR2R2) of the earth about its own axis will become one-fourth and so its angular velocity will become four times (L = Iω= constant). Hence, the time period will reduce to one-fourth (T = 2ππ/ω to), i.e. 6 hours.

Dear Student



I hope this answer will help you.
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Yash Chourasiya