Question

If the radius of the earth shrinks by 25% without change in its mass, the time duration of one day will be:

• A. 10.5 hour
• B. 12 hour
• C. 13.5 hour
• D. 15 hour

Answer 1

The correct option is C 13.5 hour

$T=24hr.$

$R^1=\frac{3}{4}R.$

$w=\frac{2\pi }{T}$

$\frac{2}{5}M{R}^2\frac{2\pi }{24}=\frac{2}{5}M(\frac{3R}{4}{)}^2\frac{2\pi }{T^1}$

$T^1=24\times \frac{9}{16}$

$=13.5hr.$