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

Explanation:

Part A

To solve this problem, I would multiply the ergs of radiant energy per second times the ergs of radiant energy in 2.45 ⋅ 105 seconds.

2.45 ⋅ 105 * 3.9 ⋅ 1033

( 2.45 * 3.9 = 9.555)

(105 * 1033 = 10^38 )

Final answer= 9.555 * 10^38

Part B:

The more reasonable measurement of the diameter of a blood cell is 7.4 ⋅ 10−3 mm. It is more reasonable because negative exponents tend to represent small numbers and positive exponents tend to represent large numbers. Since blood cells are small in size, it would make sense for 7.4 ⋅ 10−3 to represent the measurement of the diameter of a blood cell.

Answer 2

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.