problem: Taking the potential energy to be zero at infinite separation, find the potential energy of a 118.0-kg object at the surface of the earth. (Use 6.37E+6 m for the earth's radius.) I did this and got -7.374E09. It then asks Find the escape speed for a body projected from this height. I do not understand the concept of escape speed. In my book it gives this equation: sqrt 2gRe It then goes on to solve the equation to be 11.2km/s. How do I use this equation or the concept of escape speed to solve this problem. Thanks for the help.