Quiz #1 Aug 25, 2000
Show ALL work clearly for full credit!
1. [4 pts] How many arc-seconds are in 4° ?
4° x 60 arc-min/1 degree x 60 arc-sec/1 arc-min
= 14400 arc-sec
2. [6 pts] The Earth’s mass is about 6 x 1024 kg. Assume that one-third of the earth’s mass is silicon. An atom of silicon has a mass of 4.7 x 10-26 kg. How many silicon atoms does the Earth contain?
total mass of silicon = 1/3 x 6 x1024 kg = 2 x 1024 kg
# of atoms = mass of silicon / (mass of 1 silicon atom)
= 2 x 1024 kg / ( 4.7 x 10-26 kg/ atom) = 0.426 x 1050 atoms = 4.3 x 1049 atoms