An Application for Me

Message

Baker · #31 Post by **Baker** » Tue Nov 30, 2004 5:27 pm

Poo are you and PreSTO buddies? Like roommates?

Crim · #32 Post by **Crim** » Tue Nov 30, 2004 5:30 pm

A comp that can do ANYTHING? Who's it made by?

beni · #33 Post by **beni** » Tue Nov 30, 2004 5:59 pm

Poo, I'm gonna have to call you wrong on your answer. Although the radius does decrease at a constant rate, the relationship between the volume of a sphere and the radius is not linear. Therefore, your answer of 19 in^3/min is correect as the average rate of shrinkage for the first 28 minutes. However, in the next 28 minutes, the jawbreaker only shrinks at an average of 13.6 in^3/min. Therefore, the jawbreaker's decrease in size can only be expressed as an equation. Since I'm lazy, that's all I'm going to contribute for now... but since it was Poo's question anyway, I'll let someone else figure out the actual equation.

Kalign · #34 Post by **Kalign** » Tue Nov 30, 2004 10:13 pm

dig1tal wrote:good luck poo bear

lang qualifier question:
Pythagoras the Platypus is eating a really, really big jawbreaker. The jawbreaker has a radius of 7 inches. As a member of the Lang Clan, Pythagoras knows that it is against the rules to bite the jawbreaker, so he must suck on it until it is gone. Assuming that the radius decreases at a constant rate, and after 28 minutes have passed it has a radius of 6 inches, at what rate is the volume of the jawbreaker decreasing then?

r i = 7
v = 4/3 * pi * (r - t/28 )^3
v' = 4 * pi * (r - t/28 )^2 * dv/dt

there ya go

Crim · #35 Post by **Crim** » Tue Nov 30, 2004 10:46 pm

man I got 28% on my trig test... confusing! oh that was also like the average of the class (no one passed)

Poo_B · #36 Post by **Poo_B** » Tue Nov 30, 2004 10:49 pm

sorry, i didnt think too much into it, and as i always do, i read the question wrong. i wrote it down myself to figure out as the volume decreases constantly. my bad, that's why i thought it was too easy. sorry. yes, presto and i are roomies. been friends since like 9th grade. oh well. anywho, ill get back with an answer sometime, maybe

Kalign · #37 Post by **Kalign** » Tue Nov 30, 2004 11:06 pm

crim, soh-cah-toa (so-ka-toe-a), thats the main part of trig, unless you have an ass for a teacher like i did for geometry, i mean he even came in drunk a few times

digital, was that question from something or did you just make it up?

poo, yo 8)

wonder if the question can be simplified more... digital? you asked it.

Crim · #38 Post by **Crim** » Tue Nov 30, 2004 11:08 pm

SOHCAHTOA can only be used on right triangles or something, or thats pythag or something blah

Kalign · #39 Post by **Kalign** » Tue Nov 30, 2004 11:16 pm

wait i was thinking geometry wasn't i...

Presto · #40 Post by **Presto** » Tue Nov 30, 2004 11:27 pm

Kalign.Lang wrote:wait i was thinking geometry wasn't i...

Nah, geometry is all those ass sas triangle congruency laws. Can't forget proofs either. Man I hated those. Trig is pretty much sohcahtoa (and also a couple other worthless laws that suck that no one ever uses).

beni · #41 Post by **beni** » Tue Nov 30, 2004 11:39 pm

Nice work on the equation kalign... I take it you've had some calculus?

Kalign · #42 Post by **Kalign** » Tue Nov 30, 2004 11:47 pm

yeah, Mr. Pasquale in chelmsford high school is the man! First off, he starts each day with something completly unrelated to math, just current events or things he sees in the paper, or even just some fun facts, and he still teachs more than any other teacher i've ever had.

dig1tal · #43 Post by **dig1tal** » Wed Dec 01, 2004 1:11 am

Kalign.Lang wrote: digital, was that question from something or did you just make it up?

wonder if the question can be simplified more... digital? you asked it.

i pulled off the net. i didn't expect it to be answered so well. i just wanted to see if it would be answered creatively.

Poo_B · #44 Post by **Poo_B** » Wed Dec 01, 2004 8:31 am

Kalign.Lang wrote:
dig1tal wrote:

v = 4/3 * pi * (r - t/28 )^3
v' = 4 * pi * (r - t/28 )^2 * dv/dt

there ya go

i don't know if that deriv is right?? don't you need to take the deriv of whats inside the brackets as well, and multiply the whole thing by it. the chain rule or something. and why are you multiplying by dv/dt. v' = dv/dt, so if you divide it back to the other side, it'd be 1 = 4*pi... i just dont think that'd work. and can't you substitute the 7 with r, because you know the max radius, and to find any other radius, its 7 - the time thing??
idk, but oh well

Kalign · #45 Post by **Kalign** » Wed Dec 01, 2004 11:56 am

maybe i did it wrong, don't know, don't have time to check (another lab to do, shouldn't even be on the forum right now) but i did take the derivitive of the inside, v' is dv/dr in this case, not dv/dt, and thats why theres nothing about the r outside the brackets, its deriv is 1. I'm thinking maybe it should be (dv/dt)/28 though instead of dv/dt

or should it be something like dt/dr... can't remember, which goes where in the what now?