Imagine we've discovered a planet orbiting another star at 1 AU ...

[iveyjurea]

Imagine we've discovered a planet orbiting another star at 1 AU every 6 months. The planet has a moon that orbits the planet at the same distance as our Moon, but it takes 2 months. What can we infer about this planet?
 
  A) It is more massive than Earth.
  B) It is less massive than Earth.
  C) It has the same mass as Earth.
  D) We cannot answer the question without knowing the mass of the star.
  E) We cannot answer the question without knowing the mass of the moon.

Question 2

If you see Al going to your left at exactly 0.99c and Bob going to your right at exactly 0.99c, Al will say that Bob is
 
  A) going away from her at 1.98c.
  B) going away from her at exactly 0.99c.
  C) going away from her at exactly c.
  D) going away from her at about 0.98c.
  E) going away from her faster than 0.99c, but slower than c.

[upturnedfurball]

Answer to Question 1

B

Answer to Question 2

E

[iveyjurea]

Gracias!

[kusterl]

Excellent