A) A tau particle enters our atmosphere. If one such particle lives 3.00 x 10-13 s as measured from Earth, and 1.52 x 10-13 when at rest relative to an observer, what is its velocity relative to the laboratory?

v =?

B) Suppose a UFO approaches the planet Mars at v = 70% (0.700c) the speed of light and shoots an ion beam at a speed u' of 0.830c. At what velocity does a Mars bound observer see the ion beam if it is shot directly toward Mars?

u = ?