A body is projected up with a velocity equal to `3//4th` of the escape velocity from the surface of the earth. The height it reaches is (Radius of the earth is `R`)

Options

A. 10R/9
B. 9R/7
C. 9R/8
D. 1PR/3

Answer

b

Explanation

`(h)/(R)=(u^(2))/(v_(e)^(2)-u^(2))=((9)/(16)v_(e)^(2))/(v_(e)^(2)-(9)/(16)R^(2))=((9)/(16)v_(e^(2)))/((7)/(16)v_(e)^(2))=(9)/(7)`
`h=(9)/(7)R.`