A mass of `6xx10^24` kg (equal to the mass of the earth) is to be compressed in a sphere in such a way that the escape velocity from its surface is `3xx10^8ms^-1`. What should be the radius of the sphere?

Options

A. 9 mm
B. 8 mm
C. 7 mm
D. 6mm

Answer

B

Explanation

As, `v_(e)=sqrt(((2GM)/R)), R=((2GM)/v_(e)^(2)), :. R=(2xx6.67xx10^(-11)xx6xx10^(24))/((3xx10^(8))^(2))=9xx10^(-3)m=9` mm