The escape speed from a distant planet is 42 km/s. If the accelaration of gravity on the planet is 11.0 m/s/s, what is the radius of the planet?
The potential energy at the surface
GMp*m/radius but that is equal to 1/2 m vescape^2
Now you know "g", which is GMp/rad^2
or GMp=rad^2*11.0m/s
finally.
11.0* radius=1/2 vesc^2
check all that.