Question

Earth II is a planet in a distant solar system which is earth-like, but a little smaller than our earth. In the distance future, Earth II has been settled by bold travelers from our home planet. Very far from Earth II (effectively at R=∞), a spacecraft has run out of fuel and its kinetic energy is zero. If only the gravitational force of Earth II were to act on the spacecraft (i.e., neglect the forces from the sun and other solar system objects), the spacecraft would eventually crash into Earth II. The mass of Earth II is Me=4.600×10²⁴  kg and its radius is Re=5.850×10⁶  m . Neglect air resistance throughout this problem, since the spacecraft is primarily moving through the near vacuum of space.

Part A

Find the speed se of the spacecraft when it eventually crashes into Earth II.

Part B

Now find the spacecraft's speed when its distance from the center of Earth II is 12.5 times the radius of Earth II, i.e. R=αRe, where α = 12.5.

Part C

Now find the spacecraft's speed when its distance from the center of Earth II is 125 times the radius of Earth II, i.e R=αRe, where α = 125.

Answer 1