If a body is to be projected vertically upwards from the surface of the earth to reach a height nR then the velocity with which it is to be projected is

Question

\[(a)\;\sqrt {\frac{2ngR}{n+1}} \quad (b)\;\sqrt {\frac{ngR}{n-1}} \quad (c)\;\sqrt {\frac{2ngR}{n}} \quad (d)\;\sqrt {\frac{2ngR}{n-1}} \]