If astronauts could travel at v = 0.90c, we on Earth would say it ...

[B]

If astronauts could travel at v = 0.90c, we on Earth would say it takes (4.2/0.90) = 4.7 years to reach Alpha Centauri, 4.2 lightyears away. The astronauts disagree. How much time passes on the astronaut's clocks?
 a. 2.0 years
  c. 1.4 years
  b. 2.4 years
  d. 3.0 years

Question 2

A muon formed high in the Earth's atmosphere travels at a speed 0.990c for a distance of 6.40 km before it decays. What is the muon's lifetime as measured in its reference frame?
 a. 4.65  10-6 s
  c. 2.18  10-6 s
  b. 1.55  10-5 s
  d. 3.04  10-6 s

[juliaf]

Answer to Question 1

A

Answer to Question 2

D

[B]

Gracias!

[bdobbins]

Excellent