a train travels from A to B with u km/hr and back from B to A with v km/hr. what is its average speed of the whole journey?

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Basically, average speed should just be the total distance travelled divided by the time. Total distance travelled is 2 * distance between A and B. The time you can figure out in terms of u, v, and distance.

Let's call the distance between A and B d.

d = (average speed) * (time)
= u(t1)
= v(t2)

t1 = d/u, t2 = d/v

Average speed = (2d) / (d/u + d/v) = 2 / (1/u + 1/v)

That equals 2uv / (u + v) after you do the algebra on that.

EDIT:

I should note that you have to be absolutely certain that the question is asking about average speed and not average velocity, because the average velocity on this would be zero (average velocity is displacement over time, and there's no displacement).

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quote:

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Originally posted by aaqthree
Basically, average speed should just be the total distance travelled divided by the time. Total distance travelled is 2 * distance between A and B. The time you can figure out in terms of u, v, and distance.

Let's call the distance between A and B d.

d = (average speed) * (time)
= u(t1)
= v(t2)

t1 = d/u, t2 = d/v

Average speed = (2d) / (d/u + d/v) = 2 / (1/u + 1/v)

That equals 2uv / (u + v) after you do the algebra on that.

EDIT:

I should note that you have to be absolutely certain that the question is asking about average speed and not average velocity, because the average velocity on this would be zero (average velocity is displacement over time, and there's no displacement).

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Wow! AMAZING math skills, dude!

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quote:

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Originally posted by garciaas
Wow! AMAZING math skills, dude!

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quote:

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Originally posted by PsychoSnowman
haha, with the amusement that evoked in you, i am sure the "sciences" field a SHC is not missing much when you chose not to do science.

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I still have to do science. I'm taking INTEGRATED though! Why should I choose to do Biology when I did Biology already at my previous school? And the way how the system is set up.......you can't just take chemistry or physics.......you have to take all three of them...... for 2 years! I would have chosen to do the sciences, but my parents advised me and said that I SHOULD do integrated science. I always ask for their opinion. It's a wise thing to do

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quote:

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Originally posted by garciaas
I still have to do science. I'm taking INTEGRATED though! Why should I choose to do Biology when I did Biology already at my previous school? And the way how the system is set up.......you can't just take chemistry or physics.......you have to take all three of them...... for 2 years! I would have chosen to do the sciences, but my parents advised me and said that I SHOULD do integrated science. I always ask for their opinion. It's a wise thing to do

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__________________
Long messages do not equal aggravation of any sort,
rather they reflect nothing more than a response of insight
that should always be read in a matter-of-fact tone.

"Those womyn that seek equality with men, lack determination."

"I beseech you, in the bowels of Christ, think it possible you may be wrong."
-Cromwell

Last edited by PsychoSnowman on 04-19-2005 at 03:53 AM

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Eh, I took bio and AP Bio in high school, AP Bio had much, much more material in it.

Still a worthless class and an easy 5, but yeah.

I'd assume college level bio would have more material, but yeah I haven't taken that.

Physics is much, much worse in college than it is in HS, a lot more material condensed into less time.

BTW, is she still claiming to be 24/25? Or has she admitted that she's only 11 yet?

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[QUOTE]Originally posted by PsychoSnowman
[B]yeah, don't want your courseload to be too tough now do we girly? You probably should take integrated, becausei your parents obviously understand your limitations.

HA MY limitations? I don't have ANY!

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[QUOTE]Originally posted by PsychoSnowman
[B]

So many "..."'s, it makes you sound imbecillic, as if the idea of you taking...OMG....THREE science classes for two years is daunting beyond your imagination.

According to what I've heard, it is! Some TEACHERS who had taken that option said it was pretty difficult. They failed misserably. The school has a yearly parent-student conference for second year students. They spend a whole DAY warning parents and studenst about the sciences. They tell parents that if their child is getting less that 3.0 average, they should not take 3 sciences. They say how some people are "left brain" and others are "right brain". The're actually trying to terrorize the students! I'm not "afraid" or "scared" to take those subjects. Science is my 2nd favorite subject (Math is my absolute FAVORITE ever since I came to SHC). To tell you the truth, got 96% on Biology at the END of the year. Now you might say that that's nothing because the system was easy. If the system was so easy, how comes more than half of the class failed? I guess more than half of the class must be classified as "dumb."

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[QUOTE]Originally posted by PsychoSnowman
[B]

Your school is easy, i have never heard anyone say it was hard except you (heard from people who attend your school obviously). No one is impressed by the dumbass workload you have been speaking of.

You can say anything.....but there's absolutely NO proof that you've heard of the opinions of past students at SHC. Any names?

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[QUOTE]Originally posted by PsychoSnowman
[B]

What do you plan on doing after college with your major in "sciences"...become some general "scientist"? I mean, we always need lab assistants, it's cool someone wants to major in that.

My dream is to become a University Professor in the U.S. One who teaches other teachers how to teach.

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[QUOTE]Originally posted by PsychoSnowman
[B]


You took bio in high school, haha. I think bio might be the same in high school as it is in most colleges (aside from the lack of material in comparison). But, from my experience, you learn a lot more in college than they tell you in high school in regards to other sciences. I know a girl that took Organic Chemistry in high school, thinking she was the shit just becasue she all ready took it, only for her to fail so horribly it was shameful. High school was mostly a joke.

One case does not justify ALL cases!

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Who the hell has ever heard of fucking Sacred Heart College and its academic intensiveness? Is that school even ranked?

__________________
Long messages do not equal aggravation of any sort,
rather they reflect nothing more than a response of insight
that should always be read in a matter-of-fact tone.

"Those womyn that seek equality with men, lack determination."

"I beseech you, in the bowels of Christ, think it possible you may be wrong."
-Cromwell

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quote:

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Originally posted by garciaas
[QUOTE]Originally posted by PsychoSnowman
[B]

Your school is easy, i have never heard anyone say it was hard except you (heard from people who attend your school obviously). No one is impressed by the dumbass workload you have been speaking of.

You can say anything.....but there's absolutely NO proof that you've heard of the opinions of past students at SHC. Any names?

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No no no!!! i can't reveal things like names online! what if you are a serial killer or something! omigosh!!! waht are you thinking babo??!?

__________________
Long messages do not equal aggravation of any sort,
rather they reflect nothing more than a response of insight
that should always be read in a matter-of-fact tone.

"Those womyn that seek equality with men, lack determination."

"I beseech you, in the bowels of Christ, think it possible you may be wrong."
-Cromwell

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quote:

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Originally posted by garciaas
[QUOTE]Originally posted by PsychoSnowman
[B]

So many "..."'s, it makes you sound imbecillic, as if the idea of you taking...OMG....THREE science classes for two years is daunting beyond your imagination.

According to what I've heard, it is! Some TEACHERS who had taken that option said it was pretty difficult. They failed misserably. The school has a yearly parent-student conference for second year students. They spend a whole DAY warning parents and studenst about the sciences. They tell parents that if their child is getting less that 3.0 average, they should not take 3 sciences. They say how some people are "left brain" and others are "right brain". The're actually trying to terrorize the students! I'm not "afraid" or "scared" to take those subjects. Science is my 2nd favorite subject (Math is my absolute FAVORITE ever since I came to SHC). To tell you the truth, got 96% on Biology at the END of the year. Now you might say that that's nothing because the system was easy. If the system was so easy, how comes more than half of the class failed? I guess more than half of the class must be classified as "dumb."

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__________________
Long messages do not equal aggravation of any sort,
rather they reflect nothing more than a response of insight
that should always be read in a matter-of-fact tone.

"Those womyn that seek equality with men, lack determination."

"I beseech you, in the bowels of Christ, think it possible you may be wrong."
-Cromwell

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quote:

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Originally posted by PsychoSnowman
How about this, i got a perfect score in calc i, calc ii, calc iii, mechanics physics, and nearly a perfect score in Differential equations. I have gotten the high score in my physics340 class on our two midterms, and a 26% was an A in this particular class last semester (i know someone who took it last semester).

I am thinking that, yes, half the class must be dumb. What's the rank of your school again?

Biology is easy, and never anything to brag about unless you are getting into higher bio courses. Allow me to quote a tshirt i saw the other day:

"If AP chem was any easier, it'd be called AP bio"

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quote:

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Originally posted by PsychoSnowman
Who the hell has ever heard of fucking Sacred Heart College and its academic intensiveness? Is that school even ranked?

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Boy oh boy......you sure don't get it! You have to LIVE here to know about it! SHC is the best in the Cayo district in terms of not only academic excellence, but in extra-curricular activities as well!

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quote:

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Originally posted by garciaas
Boy oh boy......you sure don't get it! You have to LIVE here to know about it! SHC is the best in the Cayo district in terms of not only academic excellence, but in extra-curricular activities as well!

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Maybe you didn't know this, but Catholic schools are tough.

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quote:

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Originally posted by PsychoSnowman
No no no!!! i can't reveal things like names online! what if you are a serial killer or something! omigosh!!! waht are you thinking babo??!?

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HAHAHAHHAHAH!!!!! It's not babo, it's BOBO!!!!!!!!!!!!!!HAHAHAHAHA!

Anyways, without concrete evidence (i.e. names), you won't get ME to believe you!

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[QUOTE]Originally posted by PsychoSnowman
[B]How about this, i got a perfect score in calc i, calc ii, calc iii, mechanics physics, and nearly a perfect score in Differential equations. I have gotten the high score in my physics340 class on our two midterms, and a 26% was an A in this particular class last semester (i know someone who took it last semester).

Hell, that's easy to do! It's very easy to say all this (i.e. that you got this grade in that subject, etc.) I am simply not convinced. Try and establish "concrete" evidence. Then maybe I'll believe you. Hey, you might not even care to do so. I'm just saying this if you really want to persuade me into believing that you got "perfect scores" is a particular subject/s.

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