Question

The earth's radius is R and acceleration due to gravity at its surface is g. If a body of mass m is sent to a height of R/4 from the earth's surface, the minimum speed with which the body must be thrown to reach a height of R/4 above the surface of the earth is –

• A. $\sqrt { \frac { 2 \mathrm { gR } } { 5 } }$
• B.
• C. $\sqrt { \mathrm { gR } }$
• D.

Answer 1

Answer: (A)

$\sqrt { \frac { 2 \mathrm { gR } } { 5 } }$

Answer 2

$\frac { 1 } { 2 }$mv² = DU = $\frac { 1 } { 5 }$ mgR

v =