What would be the value of g on the surface of the earth if its mass was twice and its radius half of what it is now ?

Explanation

`g=(GM)/(R^(2))`
`therefore g_(1)=(GM_(1))/(R_(1)^(2))" and "g_(2)=(GM_(2))/(R_(2)^(2))`
`therefore" "(g_(2))/(g_(2))=((M_(2))/(M_(1)))((R_(1))/(R_(2)))^(2)=2(2)^(2)=8`
`" "(because M_(2)=2M_(1) and R_(2)=(R_(1))/(2))`
`therefore g_(2)=8g_(1)`
Thus, the, value of g on the surface of the earth woule be eight times the present value.