This upcoming week’s demo problem on relativity is:
An armada of spaceships that is 1.00 ly long (in its rest frame) moves with a speed 0.800c relative to a ground station in frame S. A messenger travels from the rear of the armada to the front with a speed of 0.950c relative to S. How long does the trip take as measured (a) in the messenger’s rest frame, (b) in the armada’s rest frame, and (c) by an observer in frame S?
To see the solution to last week’s demo problem, see the following file: Demo Problem 10-25
A write-up of how to do venturi tubes and heat engines is still in the works.