1. A person on earth notices a rocket approaching from the right at a speed of 0.81c and another rocket approaching from the left at 0.55c. What is the relative speed between the rockets as measured by a passenger on one of them?
2. Quasars are believed to be the nucleii of galacies in the early stages of their formation. Suppose that a quasar radiates electro magnetic energy at the rate of 1.5 x 1041 W. At what rate in kg/s is the quasar losing mass as a result of this radiation?