1. The problem statement, all variables and given/known data A spaceship travels from Earth to the vicinity of the star that is measured by astronomers on Earth to be six light-years away. The spaceship and its occupants have a total rest mass of 32 000 kg. Assume that the spaceship travels at constant velocity. The time taken as measured by clocks on the spaceship is 2.5 years. (i) Compute the velocity of the spaceship. [3 marks] (ii) How long does the trip take as measured by clocks in the Earth's inertial rest frame? [3 marks] (iii) What distance does the spaceship travel as measured in its own reference frame? [3 marks] (iv) Compute the kinetic energy of the spaceship in the Earth's rest frame. [2 marks] 2. Relevant equations (Lorentz transforms) 3. The attempt at a solution x=6 light years, t'=2.5 years I'm stuck on the first part of the problem. I know u=x/t, but the second part of the question asks for t, so their must be a way to find u without explicitly calculating t. Alternatively, u=x'/t', but the third part asks for x'. If anyone could give me a quick pointer that would be great. Thanks.