Asteroid Ida was photographed by the Galileo spacecraft in 1993, ...

[Tazate]

Asteroid Ida was photographed by the Galileo spacecraft in 1993, and the photograph revealed that the asteroid has a moon, which has been named Dactyl.
 
  From the dimensions of Ida and its general features, one can estimate the mass of Ida to be 4.5  1016 kg, and the distance between Dactyl and Ida is approximately 90 km. Assuming a circular orbit, what would be the orbital speed of Dactyl? G = 6.67 x 10-11 Nm2/kg2.
  A) 5.8 m/s
  B) 11 m/s
  C) 2.3 m/s
  D) 2.9 m/s
  E) 30 m/s

Question 2

Using K = 3/2 kT, what is the average kinetic energy of a He atom at:
 
  (a) 10. K?
  (b) -196.C?
  (c) 100.C?

[abctaiwan]

Answer to Question 1

A

Answer to Question 2

(a) 2.1  10-22 J = 1.3 meV
(b) 1.59  10-21 J = 0.0099 eV
(c) 7.72  10-21 J = 0.0482 eV

[Tazate]

Excellent

[juliaf]

Great answer, keep it coming