A planet has radius R R\,R and the acceleration due to gravity at its surface is ggg. What is the escape velocity for a probe of mass m m\,m when launched from an altitude equal to the planet's radius R R\,R above its surface?
gR2\sqrt{\frac{gR}{2}}2gR
gR\sqrt{gR}gR
2gR\sqrt{2gR}2gR
2gRm\sqrt{\frac{2gR}{m}}m2gR
