View Full Version : word problem(contest)

CerebralAssassin

13-01-07, 05:14

ok,there seem to be more math/physics enthousiasts here than I thought..:p

aiight folks,i got a problem for ya..so guys/gals,turn your brains up!!http://mazeguy.net/expressive/brainiac.gif

ok..here goes...suppose you have a copy of legend.suppose you have a well and you wanna determine how deep it is.the experiment is to drop the copy down the well of course.well,based on the difference of time between releasing the copy and hearing a sound from the well,determine the depth of the well

HINT:you're gonna need the speed of sound, which is 344 m/s (770 m/h)

good luck..the winner of the contest will get my utmost respect!!:)

mizuno_suisei

13-01-07, 06:55

Hi. :wve: You need to give us more info. To be able to calculate, we need two hinted values :) we dont know the Time value :)

CerebralAssassin

13-01-07, 07:07

Hi. :wve: You need to give us more info. To be able to calculate, we need two hinted values :) we dont know the Time value :)

oops..I forgot!!lol..how stupid of me...:p

the time of the sound is t=25 sec.

call the time of release t1=0:p

mizuno_suisei

13-01-07, 07:11

Ok, so D = S x T. Is it 8875m? or 88.75m? or 8.875 m :p ?

CerebralAssassin

13-01-07, 07:16

Ok, so D = S x T. Is it 8875m? or 88.75m? or 8.875 m :p ?

nope!:p

Ward Dragon

13-01-07, 07:59

Whoa, it's been a long time since I had to do an applied math or physics problem :p Through my convoluted logic, I got 2749.5 meters.

I used the physics equation s=(1/2)at^2 (s=distance, a=9.8 meters per second squared). I got that in terms of t, then added in the sound part to get

t=sqrt(2s/9.8)+s/344. I then substituted 25 for t, and manipulated it to get it into a quadratic equation:

s^2+24150.204*s-7396000=0. Then I used the quadratic formula to solve for s.

Edit: I corrected my typo in the equation

CerebralAssassin

13-01-07, 08:09

Whoa, it's been a long time since I had to do an applied math or physics problem :p Through my convoluted logic, I got 2749.5 meters.

I used the physics equation s=(1/2)at^2 (s=distance, a=9.8 meters per second squared). I got that in terms of t, then added in the sound part to get

t=sqrt(2s/9.8)+344/s. I then substituted 25 for t, and manipulated it to get it into a quadratic equation:

s^2+24150.204*s-7396000=0. Then I used the quadratic formula to solve for s.

hmm..I see a mistake..find it!!:everything else looks right!

Ward Dragon

13-01-07, 08:14

hmm..I see a mistake..find it!!:everything else looks right!

This is why I shouldn't type up math at 4 in the morning :p

t=sqrt(2s/9.8)+s/344 is what I had written on my paper. *checks if there are more errors*

CerebralAssassin

13-01-07, 08:19

This is why I shouldn't type up math at 4 in the morning :p

t=sqrt(2s/9.8)+s/344 is what I had written on my paper. *checks if there are more errors*

yeap..that's it!that's the general idea..everything after that is a piece of cake..well..you have my utmost respect!!:tmb: are you some kind of physics/math major?I knew this forum wouldn't dissapoint me!!:p

mizuno_suisei

13-01-07, 08:21

Just curious, I only learnt the Triangular DST Shape in Science last year, What IS the distance, im curious :p

Ward Dragon

13-01-07, 08:26

yeap..that's it!that's the general idea..everything after that is a piece of cake..well..you have my utmost respect!!:tmb: are you some kind of physics/math major?I knew this forum wouldn't dissapoint me!!:p

Thanks :) I'm a math and biology double major, although I haven't really seen this sort of math since high school (all of the upper level math courses were proof based with no calculations).

Just curious, I only learnt the Triangular DST Shape in Science last year, What IS the distance, im curious :p

I got 2749.5 meters (assuming I didn't make a typo while entering it into the calculator).

CerebralAssassin

13-01-07, 08:26

Just curious, I only learnt the Triangular DST Shape in Science last year, What IS the distance, im curious :p

who cares about the distance..the important thing is the process..did you get what Ward Dragon did?:p

CerebralAssassin

13-01-07, 08:31

Thanks :) I'm a math and biology double major, although I haven't really seen this sort of math since high school (all of the upper level math courses were proof based with no calculations).

I got 2749.5 meters (assuming I didn't make a typo while entering it into the calculator).

you're a math major??Gosh dang it...why didn't you say so all this time??I thought I was the only one here...I'm presently taking a course in Real analysis..how about you?:)

mizuno_suisei

13-01-07, 08:38

Can a well be 2749.5metres in Distance/Depth? Woah! I thought they werent that big xD Im not doing science this year, So I guess I wont learn much more :p Do you guys mind me giving you a Equation?

This will be easy, YR10 science for you :p

Lets say, One is in a room, and at the other end, There is a pre-released copy of TRA ^^ And you need to get there in 5seconds. Or the copy will dissapear. The Copy is 12metres away, Find out the speed in which you will need to go to get to it intime.

Ward Dragon

13-01-07, 08:39

you're a math major??Gosh dang it...why didn't you say so all this time??I thought I was the only one here...I'm presently taking a course in Real analysis..how about you?:)

I took Real Analysis last year (it was okay, but I found it to be very frustrating when the professor kept telling us we didn't know things yet so we couldn't use them in our proofs). Last semester, I took the last math class I need to complete the major. On the one hand, I'm very happy to have met all of the requirements for the math degree. On the other, it feels weird not having to take any math classes next semester (I'm taking a few classes I need for the biology and then I graduate :D)

Can a well be 2749.5metres in Distance/Depth? Woah! I thought they werent that big xD Im not doing science this year, So I guess I wont learn much more :p Do you guys mind me giving you a Equation?

This will be easy, YR10 science for you :p

Lets say, One is in a room, and at the other end, There is a pre-released copy of TRA ^^ And you need to get there in 5seconds. Or the copy will dissapear. The Copy is 12metres away, Find out the speed in which you will need to go to get to it intime.

Watch, I'll get this one wrong after getting the hard one right :p (That's always the way it is with me).

12 meters in 5 seconds is 12/5=2.4 meters per second :)

mizuno_suisei

13-01-07, 08:42

>_> You got it xD :) Your really good, did you use a Calculator? NOW Get to bed xD

Ward Dragon

13-01-07, 08:45

>_> You got it xD :) Your really good, did you use a Calculator? NOW Get to bed xD

Actually I did use a calculator :o I make random arithmetic errors even when I'm wide awake (I lost points on a midterm once because I consistently said 8+8=18 in one of the problems and I didn't have time to check everything over with the calculator...) *gets ready to go to sleep* :p

CerebralAssassin

13-01-07, 08:45

I took Real Analysis last year (it was okay, but I found it to be very frustrating when the professor kept telling us we didn't know things yet so we couldn't use them in our proofs). Last semester, I took the last math class I need to complete the major. On the one hand, I'm very happy to have met all of the requirements for the math degree. On the other, it feels weird not having to take any math classes next semester (I'm taking a few classes I need for the biology and then I graduate :D)

Watch, I'll get this one wrong after getting the hard one right :p (That's always the way it is with me).

12 meters in 5 seconds is 12/5=2.4 meters per second :)

lol..so you are ahead of me!!:p

I only have 3 300-level (advanced undergraduate) courses under my belt (but then again,I'm only a sophomore!)....2 inttro analysis courses, and a partial differential equations course!:)

it sucks that you couldn't use anything you weren't taught..I don't think my teacher will have a problem with that...were the proofs hard?:p

Ward Dragon

13-01-07, 08:54

lol..so you are ahead of me!!:p

I only have 3 300-level (advanced undergraduate) courses under my belt (but then again,I'm only a sophomore!)....2 inttro analysis courses, and a partial differential equations course!:)

it sucks that you couldn't use anything you weren't taught..I don't think my teacher will have a problem with that...were the proofs hard?:p

The difficulty level of the proofs depends on your point of view. Several of them required some obscure trick that I doubt anyone could figure out unless they saw it in a previous class. Then several of them were so painfully obvious that it was hard to put it into words. Other proofs were just brutal applications of the mathematical definitions, and a few were based upon understanding concepts. I tend to have random flashes of insight and then I get lazy writing it up, so I ended up with around a B in the class. My friend writes things out to an extreme degree (he could take 5 pages to say what I would have written in 1/2 a page :p). I remember a few problems where I explained in a few words what the general idea was, then he turned it into a novel and the teacher loved the detail in his proofs and gave him an A :p

mizuno_suisei

13-01-07, 08:56

Go To Sleep! xD Time to sleep, not time to talk xD

Ward Dragon

13-01-07, 08:57

Go To Sleep! xD Time to sleep, not time to talk xD

Alright, alright, I'm going :p (Tomorrow is Saturday so I don't need to be up anyway :))

CerebralAssassin

13-01-07, 09:00

The difficulty level of the proofs depends on your point of view. Several of them required some obscure trick that I doubt anyone could figure out unless they saw it in a previous class. Then several of them were so painfully obvious that it was hard to put it into words. Other proofs were just brutal applications of the mathematical definitions, and a few were based upon understanding concepts. I tend to have random flashes of insight and then I get lazy writing it up, so I ended up with around a B in the class. My friend writes things out to an extreme degree (he could take 5 pages to say what I would have written in 1/2 a page :p). I remember a few problems where I explained in a few words what the general idea was, then he turned it into a novel and the teacher loved the detail in his proofs and gave him an A :p

hehe..I'm just like your friend...I'm really wordy in my proofs!!everything has to be explained perfectly so that the teacher will understand!:p

hehe..well..sometimes I have flashes of inspiration.but because of the level of difficulty,I've become adept at finding proofs in other sources (books/internet).:whi:

Hurrah4Lara

13-01-07, 16:37

Good one, CA.:tmb:

I got 2749.5 meters.

t=sqrt(2s/9.8)+s/344.

Good effort Ward Dragon, cos I know you were sleepy:D. But your well is too deep though.:ton:

Your formula above is right:cool:, but with your answer of s=2749.5 in the formula, it means

t=sqrt(2x2749.5/9.8)+2749.5/344, which is 31.7.

But t is meant to be 25.

25=sqrt(2x1873.6/9.8)+1873.6/344.

So the answer is 1873.6 metres.:jmp:

You cracked it really, though, I am just tidying up:D.

H4L:wve: [Jessika]

Ward Dragon

14-01-07, 07:48

hehe..I'm just like your friend...I'm really wordy in my proofs!!everything has to be explained perfectly so that the teacher will understand!:p

hehe..well..sometimes I have flashes of inspiration.but because of the level of difficulty,I've become adept at finding proofs in other sources (books/internet).:whi:

Bah, I'm too damned honest for my own good:p (I'm the only math major I know who didn't look up the proofs online or in other books). Anyhow, if you can write things out in a lot of detail, good for you :) I'm too impatient and it's cost me more than a few points throughout my college career :whi:

Good one, CA.:tmb:

Good effort Ward Dragon, cos I know you were sleepy:D. But your well is too deep though.:ton:

Your formula above is right:cool:, but with your answer of s=2749.5 in the formula, it means

t=sqrt(2x2749.5/9.8)+2749.5/344, which is 31.7.

But t is meant to be 25.

25=sqrt(2x1873.6/9.8)+1873.6/344.

So the answer is 1873.6 metres.:jmp:

You cracked it really, though, I am just tidying up:D.

H4L:wve: [Jessika]

Good catch :) I must have entered things into the calculator incorrectly. I normally use a scientific calculator for this sort of thing, but I couldn't find it so I ended up using a graphing calculator instead (it's very good for graphs and integrals, but very bad for simple calculations).

Hurrah4Lara

14-01-07, 20:33

Good catch :) I must have entered things into the calculator incorrectly. I normally use a scientific calculator for this sort of thing, but I couldn't find it so I ended up using a graphing calculator instead (it's very good for graphs and integrals, but very bad for simple calculations).

Hehe, teamwork:hug:!

Well, I substituted sqrt(s) =y into your original equation, so it gives a simple quadratic immediately, avoiding those big numbers of yours:D! Hehe, Ward Dragon, I don't trust my calculator either!

H4L:wve:

Lara Croft!

14-01-07, 21:37

Awww...a math/physics thread???Why does that ugly part of my past has to hunt me even here?

Jacob,I hope you're not presenting your homework as a contest....LOL....kidding!!!

CerebralAssassin

15-01-07, 01:37

Awww...a math/physics thread???Why does that ugly part of my past has to hunt me even here?

Jacob,I hope you're not presenting your homework as a contest....LOL....kidding!!!

eeeee!!eisai ekso ap'to stoiheio sou edo...den nomizo einai aparaitito na sou deixo tin porta,etsi?? (lol..kidding!!):D

*cough cough*join us!!*cough cough*

you love math and physics..admit it!!:p

Cerebral Assassin, this is doing my head in - RU going to put us out of our misery?:D

So the answer is 1873.6 metres.:jmp:

I get the same - it is right, isn't it?:confused:

I substituted sqrt(s) =y into your original equation, so it gives a simple quadratic immediately

Neat! How the **** did you see that, Hurrah4Lara?!:cool:

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