very far from earth (at r=[infinity]), a spacecraft has run out of fuel and its kinetic energy is zero. if only the gravitational force of the earth were to act on it (i. e., neglect the forces from the sun and other solar system objects), the spacecraft would eventually crash into the earth. the mass of the earth is me and its radius is re. neglect air resistance throughout this problem, since the spacecraft is primarily moving through the near vacuum of space.