Question

The escape speed on earth is 11.2Km/sec.It's value for a planet having double the radius and 8 times the mass of the earth is what

Answer 1

escape velocity = √(2GM/R)
escape velocity is proportional to √(M/R)

If radius is double and mass is 8 times,
√8M/2R = √4M/R = 2√M/R
So escape velocity of planet is 2 times the escape velocity of earth

V = 2*11.2 = 22.4 km/s