Q1. An observer moving toward Earth with a speed of 0.97 notices that it takes 5min for a person to fill her car with gas. Assume, instead, that the observer had been moving away from Earth with a speed of 0.80c. how much time would observe have measured for the car to be filled in this case?
Q2. A 1000 {rm kg} wrecking ball hangs from a 15 {rm m}-long cable. The ball is pulled back until cable makes an angle of 25.0^circle with the vertical. By how much has the gravitational potential energy of the ball changed?