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Physics
OpenStudy (anonymous):

If the moon is 397,000 km from Earth, the Sun is 170,000,000 from Earth, and the speed of light is 300,000 km/s. Calculate the time it would take the light to travel: a) from the Moon to Earth b) From the Sun to Earth Show your work and please explain what you did so I can understand.

OpenStudy (vincent-lyon.fr):

You wrote "Show your work and please explain what you did so I can understand" Well, you do not seem to understand the way this website works! Please read Code of Conduct. So I return the demand to you: ""Show your work and please explain what you did so we can help"

OpenStudy (anonymous):

What I did was modify a problem in my text book by changing values so that I could see how the problem works and the solve the correct one myself.

OpenStudy (vincent-lyon.fr):

That's ridiculous! You mean you modified Earth-Moon distance !?! I already helped you with your German assignment, but you did not show much effort on your side. You cannot learn only passively waiting for other people doing the job for you.

OpenStudy (anonymous):

My physics class is in German and I can barley speak any German so I don't understand almost anything my teacher says, hence I come here and as for someone to explain what we did in class so that I get it.

OpenStudy (vincent-lyon.fr):

But the wording of your problem is in English! So you could at least attempt a simple relation between distance, time and speed? There's no German here making the problem more difficult!

OpenStudy (anonymous):

Well...if I use a distance formula I learned in math back home, I would have: \[speed * time =distance\]300,000 * x = 397,000 so 300,000x=397,000|:300,000 x=1.3233333333333333? But I'm pretty sure that isn't the formula for speed of light because when I looked it up, it gave me a really complicated equation

OpenStudy (vincent-lyon.fr):

What is the unit of x?

OpenStudy (jamesj):

To follow up on what VL is saying, the fundamental relation you are using speed x time = distance comes from the definition of speed, which is speed = distance / time Now, the units of distance you are using is kilometers, km; the units of time you are using is seconds, s; hence the units of speed is: km/s Given that, how do you interpret the 1.32 you just derived above? What are its units?

OpenStudy (anonymous):

It would be 1.32 seconds, right?

OpenStudy (vincent-lyon.fr):

Right.

OpenStudy (jamesj):

As all electromagnetic radiation--including radio waves--travels at the speed of light, this is why when we talk to people on the moon their is at least at 2.6 second pause between when you finish talking to them and they respond (skip ahead to 0:0:40 mark): http://www.youtube.com/watch?v=1Ai_HCBDQIQ (Notice also that because the sound is being recorded on earth, the pause between when the astronauts stop speaking and the President speaks again can be short, because what is being recorded of the astronauts is their transmission as it is received on earth, not as it was sent from the moon.)

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