Question

Medal!
Part A: The sun produces 3.9 ⋅ 10^33 ergs of radiant energy per second. How many ergs of radiant energy does the sun produce in 1.55 ⋅ 10^7 seconds?

Part B: Which is the more reasonable measurement of the distance between the tracks on a CD:

1.6 ⋅ 10^–3 mm or 1.6 ⋅ 10^3 mm? Justify your answer.

Answer 1

Do you know how to multiply scientific notation?

Answer 2

i have the ti-84 calculator that multiplies things

Answer 3

like this

Answer 4

Right, but we want to multiply it without expanding it. Do you know how to multiply the numbers keeping them in scientific notation?

Answer 5

no

Answer 6

Okay. First, we multiply the decimal number. After, we keep the base of ten and add the exponents (since we add exponents when multiplying the same base)

Answer 7

What do you get?

Answer 8

so do i multiply 3.9 times 1.55?

Answer 9

Yes

Answer 10

6.045

Answer 11

and with the expontents part it will be 10^40

Answer 12

Yep! So your answer is 6.045 x 10^40

Answer 13

As for part B, remember that a negative exponent on ten means that the number is less than 1 and any positive exponent is equal to or greater than 1.

Answer 14

SO i multiply 1.6 ties 1.6??

Answer 15

*multiply

Answer 16

No. It's asking you to chose between two measurements for the distance between two tracks on a CD.

Answer 17

I think 1.6 time 10^3

Answer 18

1.6 x 10^3 mm = 1.6 meters
1.6 x 10^-3 mm = 0.0016 mm.
In the scale of a CD, which one would be logical?

Answer 19

first one
?

Answer 20

Yes. But do you see why it is?

Answer 21

Yea because tracks are like the song and it takes longer time to switch between them

Answer 22

Also, because a CD is nowhere near 1.6 meters in diameter.