An alien spaceship traveling at 0.600c toward the Earth launches a landing craft with an advance guard of purchasing agents and physics teachers. The lander travels in the same direction with a speed of 0.800c relative to the mother ship. As observed on the Earth, the spaceship is 0.200 ly from the Earth when the lander is launched.
(a) What speed do the Earth observers measure for the approaching lander?
(b) What is the distance to the Earth at the time of lander launch, as observed by the aliens?
(c) How long does it take the lander to reach the Earth as observed by the aliens on the mother ship?
(d) If the lander has a mass of 4.00 x 105 kg, what is its kinetic energy as observed in the Earth reference frame?