Question

Part A: The sun produces 3.9 • 1033 ergs of radiant energy per second. How many ergs of radiant energy does the sun produce in 2.45 • 105 seconds? (5 points) Part B: Which is the more reasonable measurement of the distance between the tracks on a DVD: 7.4 • 10–4 mm or 7.4 • 104 mm? Justify your answer.

Answer 1

A perfect situation to use a proportion:

                      (3.9 x 10³³) / 1  =  X / (2.45 x 10⁵)  .

Solve that proportion for ' X ' in the usual way.
If you can't remember how to solve a proportion, then
THAT's what you have to go look up.  It's much more
important to you right now than how much energy the
sun is putting out.


7.4 x 10⁴ mm is the same size as about 243 feet !
If the tracks on a DVD were that far apart, there would not be
room for very many tracks on a DVD.  That's not reasonable.

If the tracks are  7.4 x 10⁻⁴ mm apart, then there are about
34,000 tracks in a stripe that's 1-inch wide.  I have no idea
how they do this, but it's certainly more reasonable than the
other choice.