Most people did pretty well. One error which several people made was to write 10^{1} (= 10) when they should have put 10^{0} (= 1); for example,
1.75 × 10^{1} m = 17.5 m = 57.4 ft |
Another somewhat common error was to mix units, for example:
(4.5 × 10^{9} yr) ÷ (5.7 × 10^{8} sec) = 7.9 (yr/sec) = 7.9 × (3.15 × 10^{7}) = 2.5 × 10^{8} |
My `diameter' (height), mass (weight), and age are:
D_{y} = (6 ft) × (0.3048 m/ft) = (6 × 0.3048) m = 1.83 m | |
M_{y} = (185 lb) × (0.454 kg/lb) = (185 × 0.454) kg = 84 kg | |
A_{y} = 50 years |
Dividing the Sun's diameter, mass, and age by my diameter, mass, and age, I obtain:
D_{} ÷ D_{y} = (1.39 × 10^{9} m) ÷ (1.82 m) = 7.6 × 10^{8} | |
M_{} ÷ M_{y} = (1.99 × 10^{30} kg) ÷ (84 kg) = 2.4 × 10^{28} | |
A_{} ÷ A_{y} = (4.5 × 10^{9} years) ÷ (50 years) = 9.0 × 10^{7} |
Note that the units cancel out, so the final numbers don't depend on the units used. I would have got the same final numbers with any choice of units, as long as I use the same units for myself and the Sun.
1. In which way are you most like the Sun?
2. In which way are you least like the Sun?
3. Are you surprised by your answers to the two questions above?
Joshua E. Barnes
(barnes@ifa.hawaii.edu)
Last modified: August 30, 2006 http://www.ifa.hawaii.edu/~barnes/ast110_06/homework/disc01.html |