If a planet of given density were made larger, its force of attraction for an object on its surface would increase because of the greater distance from the object to the centre of the planet. Which effect predominates?

Options

A. increase in mass
B. increase in radius
C. both effect the attraction equally
D. none of the above

Answer

A

Explanation

Let R be the original radius of a planet then attraction on a body of mass m placed on its surface will be
`F=(GM'm')/(R^(2))`
If size of the planet is made doubel i.e R=2R then mass of the planet becomes
New force `F=(GM'm)/(R^(2))=(G8Mxxm)/(2R^(2))=2F`
i.e force of attraction increases due ot the increases in mass of the planet