The escape speed of a body on the earth's surface is `11.2kms^(-1)`. A body is projected with thrice of this speed. The speed of the body when it escape the gravitational pull of earth is

Explanation

Here, `upsilon_(e) = 11.2 km s^(-1)`, Velocity of projection of the body `upsilon = 3 upsilon_(e)`. Let `m` be the mass of the projectile and `upsilon_(e)` be the velocity of the projectile when far away from the Earth (i.e., out of gravitational field of Earth).
Then, from the law of conservation of energy
`(1)/(2) m upsilon_(0)^(2) = (1)/(2) m upsilon^(2) - (1)/(2) m upsilon_(e)^(2)`
or `upsilon_(e) = sqrt(upsilon^(2) - upsilon_(e)^(2)) = sqrt(8) xx 11.2 = 31.68 km s^(-1)`