UPSB v4
Off-topic / math help?
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Date: Fri, Jan 21 2011 19:48:03
heres the question: If a ball is thrown straight up into the air with an initial velocity of 50 ft/s, it height in feet after t second is given by y=50t–16t^2. Find the average velocity for the time period beginning when t=2 and lasting 1) 0.1 seconds 2) 0.01 seconds 3) 0.001 seconds if you can just show me how to get one of the answers, id be grateful :) thanks! btw, ive already tried deriving it then plugging in 2 then dividing the total by 0.1, 0.01, and 0.001. they all didnt work... Also how do you solve limit (64-y)/(8-y^(1/2)) y > (approaches) 64 lmao, yes, im bad at math
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Date: Fri, Jan 21 2011 20:31:20
use calculus, if you have a position function the dervitive will be the velocity function v=50-32t just plug in the number you need into that and you'll be good. For the averages just be plug in 2 and 2.01 (etc.)add the two answers together and divide by two. EDIT: and for the limit you just let y=64 you get 0/0 so the limit approaches 0. if the numerator isn't zero thats when you have to worry about algebra and manipulating the denominator out. EDIT EDIT: My limit thing is flat out wrong, ignore it
SJ wrote: heres the question: If a ball is thrown straight up into the air with an initial velocity of 50 ft/s, it height in feet after t second is given by y=50t–16t^2. Find the average velocity for the time period beginning when t=2 and lasting 1) 0.1 seconds 2) 0.01 seconds 3) 0.001 seconds if you can just show me how to get one of the answers, id be grateful :) thanks! btw, ive already tried deriving it then plugging in 2 then dividing the total by 0.1, 0.01, and 0.001. they all didnt work... Also how do you solve limit (64-y)/(8-y^(1/2)) y > (approaches) 64 lmao, yes, im bad at math
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Date: Fri, Jan 21 2011 21:10:18
For the first part you can use the Average value function: (1/b-a)*(Integral from a to b of the function) so just do that for the velocity (derivative of position) For the second part use L'Hopital's rule, the limit for f(x)/g(x) = the limit for f'(x)/g'(x) so for your example the limit of (64-y)/(8-y^(1/2)) = limit of -1/(-(1/2)y^(-1/2)) (aka the derivative of the top over the derivative of the bottom) @SJ I just described how to do them now you can try yourself, if you still need help let me know
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Date: Fri, Jan 21 2011 21:22:56
dude, not cool, he just says he isn't good at math so you give him theorems and say you described how to do it. He obviously doesn't have the mathematical background you have, I doubt he is going to understand your post. Look at the question he's trying to solve, I had to wonder "Is calculus allowed?" you need to be decent in math before your post makes the problem any easier lol.
strat1227 wrote: For the first part you can use the Average value function: (1/b-a)*(Integral from a to b of the function) so just do that for the velocity (derivative of position) For the second part use L'Hopital's rule, the limit for f(x)/g(x) = the limit for f'(x)/g'(x) so for your example the limit of (64-y)/(8-y^(1/2)) = limit of -1/(-(1/2)y^(-1/2)) (aka the derivative of the top over the derivative of the bottom) @SJ I just described how to do them now you can try yourself, if you still need help let me know
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Date: Fri, Jan 21 2011 21:27:08
Awesome wrote: dude, not cool, he just says he isn't good at math so you give him theorems and say you described how to do it. He obviously doesn't have the mathematical background you have, I doubt he is going to understand your post. Look at the question he's trying to solve, I had to wonder "Is calculus allowed?" you need to be decent in math before your post makes the problem any easier lol.
@Awesome: um wtf are you talking about? those are both basic calc 1 questions that get asked in every calc 1 class, and i gave the basic calc 1 answers that are taught in every calc 1 class ... average value theorem and l'hopitals rule are like the simplest calc 1 rules plus, the descriptions i gave him actually give him the right answers <_< -
Date: Fri, Jan 21 2011 21:34:15
@strat1227 obviously, and if he got them why would he make a post asking for help? Not everyone is pro at math. Its like you say "Hi I am not good at french" and someone starts speaking french to you.
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Date: Fri, Jan 21 2011 21:36:17
Awesome wrote: @strat1227 obviously, and if he got them why would he make a post asking for help? Not everyone is pro at math. Its like you say "Hi I am not good at french" and someone starts speaking french to you.
not being good at something doesn't mean you're an idiot... the fundamental of learning anything is to be provided the basics to get started then you should be able to figure out. -
Date: Fri, Jan 21 2011 21:36:21
@Awesome he asked how to do them, i gave him formulas where all you have to do is literally plug in the numbers and it spits out the right answers, i have no idea how to make it more simple than that without doing it for them the way he worded it sounded like he wasn't sure what the first steps he should take should be "If you can just show me how to do it i'd be grateful", so I showed him what direction he should head in the answers you gave had nothing to do with calc 1 and if he put those down he wouldn't get them right, i showed him how to get the answers, dunno what else i could have done to help
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Date: Fri, Jan 21 2011 21:39:23
look at his post, hes having trouble with some basic concepts/fundamental understating of what he's doing
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Date: Fri, Jan 21 2011 21:41:36
@Awesome ok here, this is clearly what you want me to do to help him so i'll do it:
is that clear enough? i'm sorry but if someone literally goes step-by-step and solves it, that's not "help" thats doing it for him. -
Date: Fri, Jan 21 2011 21:45:31
*sigh* I meant if you want to help someone who isn't good in math you are going to have to use some not math terms to help them out. I am not bad in math, not the greatest, but I always find the textbook explanations hard to follow, some explanation of what happening is always nice.
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Date: Fri, Jan 21 2011 21:46:52
lol but the way you told him was just plain wrong! i don't understand what you want me to do, i gave him an explanation of how to solve it and you said i wasn't being fair, i give him step-by-step and you still say i'm doing it wrong i'll just wait and see what SJ says about it.
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Date: Fri, Jan 21 2011 21:51:33
I never said you were doing it wrong lol. What I am saying is if you want to teach someone something they are struggling with you probably want to tone the technicality down from what they were receiving, not go into the same level they had trouble with. I have no problem with what you are doing, just that you don't seem to realize not everyone is as capable as you are mathematically. But yeah lets see what SJ has to say.
strat1227 wrote: lol but the way you told him was just plain wrong! i don't understand what you want me to do, i gave him an explanation of how to solve it and you said i wasn't being fair, i give him step-by-step and you still say i'm doing it wrong i'll just wait and see what SJ says about it.
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Date: Sat, Jan 22 2011 02:06:17
Determine the Coefficient of x^ 12 in [(2x^2) - (1/x) ]^12 Any help? ASAP pl0x
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Date: Mon, Jan 24 2011 04:15:04
ok this thread got a little heated..... lol i managed to get the answer for the first one. second one i still dont get it. we "supposedly" havent learned lhospitals yet. so how do you solve it w/o using that? tbh, awesomes response was easier to understand. strat, i tried using the average value theorem but it didnt work lol thanks for the help guys. you guys are both right. i dont have a strong basis in math and by that i mean im not an expert of any sort... especially in calc LOL its easier for me if you can explain in simple terms but at the same time i dont want you to do it for me. i hope you get what i mean.
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Date: Mon, Jan 24 2011 04:49:27
@SJ it might look heated but me and strat and buds, its how we roll :P for the limit you can rationalize the denominator (in this case, multiply by (8+y^1/2)/(8+y^1/2)) this helps you get rid of the denominator, then you are no longer dividing by zero. when you do so, you should be able to get it to 8+y^1/2 then you can just let y=64.