Physics Problem Perhaps you could help we with

[Wicked Pilot]

An observer detects two explosions that occur at the same time, one near her and the other 100km away. Another observer finds that the two explosions occur 160km apart. What time interval seperates the explosions to the second observer?


I got 4.16*10^-4 seconds. Anybody get anything different?

[Sonnenburg]

I asked the one near the explosion. She said. "OH MY LEGS!! MY GOD I CAN'T FIND MY LEGS!!!!!!!!!!!!!"

Results: Inconclusive.

Solution: Find another annoying pop star and have her observe an explosion up close.

[Slartibartfast]

*POKE*

[Asst. Asst. Lt. Cmdr. Smi]

The answer, the same as it is in any algebra problem, is "who gives a ".

[XaLEv]

The answer, the same as it is in any algebra problem, is "who gives a ".

Did you say damn, shit or fuck there?

[The Dark]

The answer, the same as it is in any algebra problem, is "who gives a ".

Did you say damn, shit or fuck there?

I think it was f*** (not typing it out in case it was modded for some reason). Personally, I like "rat's ass" better.

[XaLEv]

I think it was f*** (not typing it out in case it was modded for some reason). Personally, I like "rat's ass" better.

Smi has some software on his computer that censors his posts. Takes out murder and terror, too. I'd be interested in seeing a full list of what it censors.

[The Dark]

I think it was f*** (not typing it out in case it was modded for some reason). Personally, I like "rat's ass" better.

Smi has some software on his computer that censors his posts. Takes out murder and terror, too. I'd be interested in seeing a full list of what it censors.

I thought I saw the word up when I originally read the post...maybe I was hallucinating or something.

[C.S.Strowbridge]

I asked the one near the explosion. She said. "OH MY LEGS!! MY GOD I CAN'T FIND MY LEGS!!!!!!!!!!!!!"

Results: Inconclusive.

Solution: Find another annoying pop star and have her observe an explosion up close.

Oh dear god, this forum is going to hell in a handbasket. So it will be no better than ASVS. .... I wonder if I should start my takeover plan now, or wait till after Christmas.

[Zoink]

They should have spent less time telling you about the first observer, and more time telling you what the atmospheric conditions are. You need the local speed of sound, divide 160km by the speed of sound and you'll get the time interval.

So if the local speed is 331m/s = 0.331km/s, then the time interval is 160km / .331 km/s = 483 seconds.

It all depends on the speed of sound.

[The Dark]

They should have spent less time telling you about the first observer, and more time telling you what the atmospheric conditions are. You need the local speed of sound, divide 160km by the speed of sound and you'll get the time interval.

So if the local speed is 331m/s = 0.331km/s, then the time interval is 160km / .331 km/s = 483 seconds.

It all depends on the speed of sound.

It might be speed of light instead. Observing might not necessarily be hearing, but rather seeing the explosions. Unfortunately, I have a class to attend, or I would do the calcs.

[Durandal]

In this case, observing is seeing the explosions, and that's how you're supposed to do the problem.

I started it last night, but just got tired and went to bed. Anyway, using the first observer's information, you'll see that the second explosion, according to the first observer, takes place about 5.33E-5s after the first one.

It also depends on where the second observer actually is. Zoink assumed that the second observer was right next to the first explosion, but that's where the first observer was, and according to her, the explosions were 100km apart.

[Zoink]

In this case, observing is seeing the explosions, and that's how you're supposed to do the problem.

The wording isn't clear. The "time interval seperat[ing] the explosions to the second observer" would be when the actual explosion reaches the observer. That wouldn't be until the shockwave gets there.

You could take it as being the interval that he can visually see the explosions... but again its not clear.

It also depends on where the second observer actually is. Zoink assumed that the second observer was right next to the first explosion, but that's where the first observer was, and according to her, the explosions were 100km apart.

No, the explosions are 160km apart. The observer#1 is 100 km from one explosion, with the other being closer.

I never assumed that the second observer was next to the first explosion. There isn't enough information to locate the second observer. The question asks for the interval between arrivals, it might take 1 hr for the first to reach him, with the second explosion arriving sometime after that.

If the second observer is simply visually determining that the relation between the explosion themselves (160km), that that doesn't specify the location of the second observer, and it is therefore impossible to determine the arrival time of light, sound, anything. Depending on his position, he could see them arrive at the same time!

----

We need locations for observer #1&2 and explosion #1&2. If you take AutoCAD (for example) and:

- draw a 100 unit line, one end being the observer#1 and the other being explosion #1. This located those two.
- draw a 100 radius circle from observer#1, explosion #2 is somewhere within that circle.
- draw a 160 radius circle centered on explosion #1, explosion #2 is somewhere on that circle (because they're 160km apart).
- the second explosion is on the line of the second circle that is within the first circle. So explosion #2 is still not determined, and we still have no idea where observer #2 is.

What I did was assume the second observer was determining distance from the arrival time, that he measured the time interval and calculated that "the second explosion is 160km more distant". If you want it for light, then divide by the speed of light instead of sound.

I would ask Wicked Pilot to check the wording to make sure he's not missing something... unless I am, but I don't see it.

[Darth Wong]

An observer detects two explosions that occur at the same time, one near her and the other 100km away. Another observer finds that the two explosions occur 160km apart. What time interval seperates the explosions to the second observer?

OK, if observer 1 is very close to explosion A, then her perceived distance to explosion B (100km) should be the true distance between A and B. Therefore, there is no reason why observer 2 should perceive explosion A to be 160km away from explosion B. No matter what his viewing angle is, the explosions might appear to be closer, but not farther away from one another.

Barring time/length dilation at high relativistic speeds, I don't understand how this question works. Did I miss something?

[Wicked Pilot]

This is a relativity problem. Unfortunately, the origional answer has since been turned in. There is no real need to solve this problem anymore, unless you simply want to do it for yourself.

[Durandal]

An observer detects two explosions that occur at the same time, one near her and the other 100km away. Another observer finds that the two explosions occur 160km apart. What time interval seperates the explosions to the second observer?

OK, if observer 1 is very close to explosion A, then her perceived distance to explosion B (100km) should be the true distance between A and B. Therefore, there is no reason why observer 2 should perceive explosion A to be 160km away from explosion B. No matter what his viewing angle is, the explosions might appear to be closer, but not farther away from one another.

That's exactly what I was thinking. Then I figured that it must be a problem involving special relativity, given that there is no preferred frame of reference in special relativity.

Barring time/length dilation at high relativistic speeds, I don't understand how this question works. Did I miss something?

I don't think so. It's just not a very well thought-out problem. The problem should have stated if one of the observers was moving at relativistic velocity.

Wicked, how did you go about solving it?

[Wicked Pilot]

Wicked, how did you go about solving it?

Spacetime interval: All observers in inertial frames measure the same interval (s) between pairs of events in spacetime, where (s)^2=(ct)^2-(x)^2




Perhaps I should have asked Jonathan. He seams to be the rational physicist among us

[Durandal]

John probably could have helped you out; he's just a moron when it comes to his faith, and his views are a mangled mess of contradiction.

Although, I do remember when he tried to prove that "gravitational fluctuations" meant "super-intense gravity" to try and send photon torpedo firepower figures through the roof. That was funny.

[Darth Wong]

Let's not forget that he was one of the progenitors of the "Skin of Evil" stupidity, in which a brief flash was assumed to be a monstrous multi-teraton blast fireball (even though such a blast would last for many minutes rather than <1 second).

[Durandal]

<sniff>

Ah, the goold ole days...

[Jonathan]

John probably could have helped you out;

Unfortunately, I was too busy with other things to notice the question until it had been answered. Sorry about that. Come to think of it, I'm still busy. Oh well, just have to remain sane for another 18 days, then I'm free once more.

he's just a moron when it comes to his faith, and his views are a mangled mess of contradiction.

Nonsense. It's entirely self-consistent. You just don't agree with it. That doesn't necessarily make it wrong or illogical.

Although, I do remember when he tried to prove that "gravitational fluctuations" meant "super-intense gravity" to try and send photon torpedo firepower figures through the roof. That was funny.

Actually, that's not entirely true and a I later conceded the point when it was pointed out that I got the time of a crucial piece of evidence wrong. You can't summarise the whole thing in one line like that. You'd have to re-read the entire thread.

[Jonathan]

Let's not forget that he was one of the progenitors of the "Skin of Evil" stupidity, in which a brief flash was assumed to be a monstrous multi-teraton blast fireball (even though such a blast would last for many minutes rather than <1 second).

That's not true. I wasn't involved in calculating stuff for that one.

[Jonathan]

Wicked, how did you go about solving it?

Spacetime interval: All observers in inertial frames measure the same interval (s) between pairs of events in spacetime, where (s)^2=(ct)^2-(x)^2




Perhaps I should have asked Jonathan. He seams to be the rational physicist among us

I'm curious, are you doing a physics degree at the moment if you're having to answer these questions? If so, what kind and where? Just curious about what kind of things everyone here is up to.

[Malecoda]

It's a trick question. The first sentence says they were 100 km apart. A second sentence says 160. How does the perception of any observer change the distance if it's given?

[Durandal]

Distance is relative, and length dilates at relativistic speeds.