You launch an engine-less space capsule from the surface of the Earth and it travels into space until it experiences essentially zero gravitational force from the Earth. The initial speed of the capsule is 18,500 m/s. What is its final speed? Assume no significant gravitational influence from other solar system bodies. The Earth's mass is 5.97×10^24 kg, and its radius is 6.38×10^6 m. I have no idea where to start on this problem. Any help?