Suppose that Mercury grew to its present size in 1 million years ...

[jparksx]

Suppose that Mercury grew to its present size in 1 million years through the accretion of particles averaging 100 g each. On average how many particles did Mercury capture each second? Note: Mercury has a mass of 3.3  1023 kg and a radius of 2439 km.
 
  a. about 24 particles per second
  b. about 3.3  1021 particles per second
  c. about 67 particles per second
  d. about 100 million particles per second
  e. about 100 billion particles per second

Question 2

The speed of the solar wind is approximately 400 km/s and the distance from the Sun to Saturn is 9.5 AU (1 AU = 1.5  108 km). How long does it take a particle in the solar wind to reach Saturn?
 
  a. about 4.1 hours
  b. about 4.1 days
  c. about 41 days
  d. about 4.1 years
  e. about 41 years

[Alyson.hiatt@yahoo.com]

Answer to Question 1

e
RATIONALE: Using conversions, you can set up an equation like total mass = (mass/time)  time or 3.3  1023 kg = (mass/time)  1 million years to get (mass/time) = 10 billion kg/s. But the answer they want is in particles/s so write another equation where (particles/time) = (mass/time)/mass or (particles/time) = 10 billion kg/s/0.1 kg or (particles/time) = 100 billion particles/s

Answer to Question 2

c
RATIONALE: Using conversions, you can set up an equation like t = d / v = 9.5  1.5  108 km / 400 km/s to obtain the time in seconds and then convert the time to days.

[jparksx]

TYSM

[cdmart10]

Excellent