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The mass density of a planet of radiu...

The mass density of a planet of radius R varie with the distance r form its centre as `rho (r) = p_(0) ( 1 - (r^(2))/(R^(2))) `. Then the graviational field is maximum at :

A

` r = sqrt((5)/(9))R`

B

` r= (1)/(sqrt(3)) R`

C

`r = R`

D

` r = sqrt((3)/(4))R`

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