A block hole is a body from whose surface nothing may even escape. What is the condition for a uniform spherical body of mass `M` to be a block hole? What should be the radius of such a black hole if its mass is nine times the mass of the earth?
Mass of earth `= 6xx 10^(24)kg`,
`G = 6.61 xx 10^(-11) Nm^(2) kg^(-2)`.