The escape speed of a particle on the surface of the earth is 11.2km/second. A body is projectwith thrice this speed from the surface of the earth. What is the speed of the body in the outer space far away from the earth?

Options

A. `22.4km//s`
B. `33.6km//s`
C. `31.7km//s`
D. `5.6km//s`

Answer

C

Explanation

Initial K.E. `=9((1)/(2)mv_(e)^(2))`.
When it escapes from the influence of the earth,
`(1)/(2)m(V^(1))^(2)=9((1)/(2)mV_(e)^(2))-(1)/(2)mV_(e)^(2)`
`therefore V^(1)=sqrt(8)V_(e)=31.7 km//s`