Light Speed

1. Feb 20, 2008

zachcumer

The Sun is 1.5 x 10^11 m from the Earth. How long does it take for the Sun's light to reach the Earth?

Above is the question I have to answer I was thinking....

300,000,000,000 meters/1.5*10^11....dunno?

2. Feb 20, 2008

chroot

Staff Emeritus
Look at the units:

$1.5 \cdot 10^{11} \,m \cdot \frac{ 1 s }{ 3 \cdot 10^8 \,m }$

Note that the meters cancel, leaving you with seconds.

If you divide it your way, you get:

$\frac{ 3 \cdot 10^8 \, m }{ 1 s} \cdot \frac{1}{ 1.5 \cdot 10^{11} \,m}$

which has units of 1/s. This isn't a unit of time, so it's not what you want.

- Warren

3. Feb 20, 2008

zachcumer

so.........

4. Feb 20, 2008

chroot

Staff Emeritus
Yes?

- Warren

5. Feb 20, 2008

zachcumer

I need it in minutes not seconds.?

6. Feb 20, 2008

zachcumer

so the answer is 5 times 10 to the 18?

7. Feb 20, 2008

Integral

Staff Emeritus
No, you may need to review how to multibly and divide exponents.

8. Feb 20, 2008

zachcumer

so its 500 seconds...

9. Feb 20, 2008

chroot

Staff Emeritus
Yes, that's correct.

- Warren