Math Problem

I need a formula to answer a question such as this: If a 7 feet 300 lb man can have 24 beers before becoming intoxicated, how many beers can a 5 feet 100 lb man consume before becoming intoxicated. Or direct me to a site where I might have this answered. Thanks in advance.

Topic by Sovereignty   |  last reply


Simple math? Answered

This is one of those crazy things put up on Facebook. From what i can tell most people are getting this wrong. But you follow the rules for simple math -- Rule 1:   First perform any calculations inside parentheses. Rule 2:   Next perform all multiplications and divisions, working from left to right. Rule 3:   Lastly, perform all additions and subtractions, working from left to right. So it is       3-18+2= -13    And yet people think I am wrong ??   I simplified it even more for them ---- 3+2 =5     5-18= -13  Why are so many getting this wrong?  Or maybe I am wrong---- time to go back to grade school I guess.

Question by Vyger   |  last reply


Math question

I need help on this question, it come sup often in one form or another in mathcounts, so I need to know how to solve it There are 5 letters, 3 of each, take out 10. AAA, BBB, CCC, DDD, EEE. You do not replace letters after taking one out, and order does matter. How many ways to arrange the letters are there?

Topic by starwing123   |  last reply


math fromula

Thought this would be an appropriate place to share some of what i thought was interesting information to do with the area of a triangle and how numbers co-relate. To round off a square to 100cm square, one quarter of that area is 25cm square, (10cmx10cm =100/(div)25%=25cm), the area of a  right angle triangle with sides measuring ~7.0710cm,  equals ~25% of 100cm square,  25cm square of area,  (7.0710/2=3.5355 x7.0710=24.9995205). 7.5937 if it is an equilateral triangle. it is a standard size i use,  a handy measurement if you use templates for construction because it in  some way represents a metric increment, thanks, Kim (the formula i used is half the base times the height,  unless im mistaken i recall that is the correct formula?  though i am not a full time mathamatician.  for the equalateral triangle i used a web based polygon area calculator.)

Topic by QSDR   |  last reply


A math challenge...

Ok, so there's this coding language called FCML- a simple language built for a scripting engine in a game (Fantastic Contraption). I'm wanting to write a script that implements the graph of an equation in the form of axn+b to that gaming language. To clarify, this is to create a "level", or a series of bricks, and fitting them along the line of a user-specified equation. The coding language is very simple:StaticRect (x1, y1), (x2, y2), zWhere x1 and y1 are coordinates on a Cartesian coordinate plane, x2 and y2 are lengths and widths of the rectangle, respectively, and z is the rotation of the brick. The brick is positioned with respect to it's center; i.e. it's center is positioned with x1 and y1. It's mathematically possible; it's just very confusing for a 7th grader. With a little calculus, trigonometry, and algebra I've come up with these formulas, and would just like to see what others come up with before implementing them.Input: y=axn90-tan-1(1/naxn-1) for z10 for y2root((axn-a(x-.5)n) + .25) for x2axn+.5(axn-a(x-.5)n) for y1x - .25 for x1I'm aiming for an accuracy of 1/2.

Topic by Padlock   |  last reply


Math Problem Answered

What will be the equation for y for the following graph? y=5, x=0 y=4, x=1 y=3, x=2 y=2, x=3 y=1, x=4 y=0, x=5

Question by Wisaam   |  last reply


Math riddle? Answered

My friend asked me this one, I couldn't figure it out but I think the question itself is somehow flawed.Anyway, so here it goes: A kid has to buy a toy of 100 Rupees, he takes Rs.50 from his father and 50 from his mother. Later when he goes to the store he finds that the toy is only 97 rupees, he buys the toy and 3 rupees are left, still with me? Now he goes to his mother and father and out of those 3 rupees gives one rupee to his father, one rupee to his mother and keeps the remaining 1 rupee aside (not for himself). Now here is the question, as he has already given 1 rupee to his mother and father each, he has remaining 49 rupees to pay each one, so, my friend asks that add 49 to 49, 98, and then add to it the remaining 1 rupee he had kept aside, 99. Where did the remaining 1 rupee go? I just can't understand what is he trying to ask, the calculation he just did, I think, has nothing to do with amount the kid has to pay or paid.

Question by the-science-dude   |  last reply


Math / word question

If I had a million dollars and spent one thousand dollars a day,how many years would it take to spend the million dollars?

Question by suer69   |  last reply


math/school help

I need some help in school. today, we had an exam. our teacher did a very bad job explaining the subject matter, and i could barley hear her over everyone talking. the manual i have for math did not explain anything either. anyhow, i probably didnt do too well on the exam.what should i tell my parents? they have a hard time believing that the teacher is at fault too. any help?

Topic by tech-king   |  last reply


Determining Distance With Math? Answered

Ok, I am only a freshman in high-school so I have know idea how to determine how high an object will travel at a given weight and size.  Does anybody know what this math is called and were I can learn it.

Question by jj.inc   |  last reply


Alice in Wonderland & maths?

In New Scientist No2739/40/41 (Christmas 2009) is an article by Melaine Bayley (DPhil Oxford) in which she explains how Lewis Carroll (Charles Dogson) is taking a stab at the new mathematics of the time in his famous work. For example, the Mad Hatter's Tea Party is related to Hamilton's maths. Interesing stuff (to me anyway...) Read here

Topic by lemonie   |  last reply


LED Math Help

I want to create a LED grow light but i am having trouble with the math. I have 5 blue LEDs that are 3w( Vf: 3-3.4 v and If:700ma). Now i want to wire these in a series. So if i were to use two of these for example, would it require more volts and the same current. So: 2@3v = 6v @700ma. 

Question by Lord_Tryndamere   |  last reply


Calculator Programs for Math

I've been working on some programs for my calculator recently and have decided to share them. I made these myself from scratch. If you want to modify go ahead just credit me. Don't sell them. And don't use them in math class if your teacher says not to. The programs are a follows: a quadratic formula solver, parabola solver, slope of a linear equation finder, and y-intercept finder. The programs work on TI-83's and TI-84's. If you have questions on how to use them or how to put them on your calculator please leave a comment!

Topic by sardines454   |  last reply


Oscillator Trouble/Math ?

I have a "step-up" transformer from a DVD player that I really want to experiment with, but I know I need some form of alternating current to use it. I just finished taking a 3-week summer camp at which I learned about electronics, and there I encountered the 555 circuit. It's simple to build; I can just connect all the pieces on a small breadboard, considering I have several 555 chips. But what makes me a little miffed is that anything over 6V could burn out the chip's components. So I gave up on the 555 oscillator, and turned to the simple(-er) LC circuit. I want to have around 60 Hz to simulate the mains frequency, but I have no idea what capacitance or inductance I should use. Furthermore, I don't quite understand how to achieve a specific inductance based on coil turns, coil diameter, coil length, etc. If anybody could clear me up on these concepts, I'd greatly appreciate it.

Question by Umniscient 


Do we need math?

So, do we need math? As if you didn't know my question from the title...

Topic by Squaggadoodle   |  last reply


Integrating Math into My Programs?

First off, let me just say I love numbers.  Absolutely love them.  Unfortunately, I don't particularly have the know-how (possibly ingenuity) to integrate it into my programming beyond a few variables for text-based games.  Do you know of any good ways to do this for say, gravity simulations and such?  Links are always welcome. Thank you! 

Question by StarscreamClone   |  last reply


Math wiki formatting on instructables

Alright Instructables, I fold. It is with a sense of shame that I must ask: Does Instructables have a method (be a clandestine feature or a workaround) to allow a user to enter formatted math text (ex. summation signs, integrals, greek letters even)? In particular, I was trying to get latex to work (I thought I had seen another user do so once) on the wiki, but thus far my efforts have proved fruitless. Anyone out there know a way to do this?

Topic by purduecer   |  last reply


"Knex War?" (The Math Bit)

Hey guy! Sharir1701 here and I just want to start off by saying that I'm not back into Knex warfare, but I have something to show you. About a year and a half ago, I posted this forum topic. There I explained why, in my opinion, just adding more rubber bands to a gun will not actually produce an overall better gun (past a certain, low point). I'm not getting back into that discussion, but I simply wanted to share something regarding that. Don't ask me how or why (I don't know, myself), but a few days ago I suddenly remembered that old assumption I made. Being a perfectionist, I hate leaving things unfinished or unexplained (particularly math and physics related inquiries). Back when I posted that topic, I had little to no formal Physics knowledge, and the beginnings of an understanding in mathematics. Now, I have a much broader understanding, much more knowledge, and an ability to explain and evaluate what I once couldn't. Anyway, what I'm trying to say is, back then, I didn't have the tools to prove my claims. I firmly believed in them, but I couldn't confirm them. It's nothing complicated, but, like I said, just something I'd like to share. I also want to point out that, although I personally don't enjoy spending days upon days perfecting a little plastic mechanism for firing (mostly) non-aerodynamic plastic projectiles, anymore, there still is a warm spot in my heart for the craft I once loved. More to the point - this is a small article just showing something I did in a few minutes the other day, that helps me to better understand how a Knex gun works. I hope that in writing this, more people that are still building guns, will think about more accurately calculating certain things about their guns to help improve their performance and hopefully produce more efficient guns. The final note I have is that I'm about to show you equations, all of which can be plugged with real, measurable numbers, to calculate to a high degree of accuracy, the forces at play. This means you can actually calculate the most efficient layout for a gun, and also that in designing your next, you will be able to use these equations, and many others, to find optimal solutions to your problems. So, what's all this fuss about? Well, basically, I just proved with a few, painfully easy equations that my conjecture about the forces in a gun, working on the pin, is true. I'll just get to it: First, Hooke's Law states that the force necessary to change the length of a spring or a (tense) rubber band is F=K*dX, where F is the force, dX is the distance you want to change, and K is a constant number, that each rubber band (or spring) has. You can quite easily measure both of these. For rubber bands connected parallel to each other (assuming they are the same type of rubber band, which ever is your chosen standard), this equation becomes F=K*dX*N, where N is the number of rubber bands used. dX and K are both constant in the regards of the pull of a pin on a standard Knex pin gun. Therefor, the amount of force required to cock a pin (pull it back to it's full length) is linearly correlated to the number of bands you put on your gun. Next, if we examine Newton's equation of work and energy, W=dE=F*dX, where W is the work, dE is the change in energy in your system (input from an external force, i.e. your hand), F is the force applied along a length of movement, and dX is that length. Let us define the base position of the pin (not cocked, minimum tension on the rubber bands, fully in the barrel, etc.) as having 0 energy. This then means that the work applied to the pin by cocking it is equal to all the potential energy it has. From this, plugging in the force, we get Ep=K*(dX)^2*N. Let us assume a perfect world, where we neglect the effects of friction and air resistance, and assume all the momentum of the pin is transferred into the bullet as it fires (I will briefly mention in the end, why everything we're neglecting here just strengthens my claim in reality, but let's continue for now). After being released (in other words, shot), the maximum velocity the pin reaches right before the end of it's journey can be found using the equation for kinetic energy Ek=1/2*M*(Vmax)^2, using the fact that (again, neglecting energy wasted as heat due to friction) the energy is conserved, as no external force is working on the system, which then means that Ep,start=Ek,end => K*(dX)^2*N=1/2*M*(Vmax)^2 => Vmax = sqrt(2*K*(dX)^2/M) * sqrt(N). The first sqrt term in the final equation is all one big constant (again, K is the ratio associated with the rubber band, dX is the distance the pin travels, and M is the mass of the pin), meaning we can conclude that (C for constant) Vmax=C*sqrt(N). Finally, force applied by a moving, massive object can be calculated using Newton's second law, F=dP/dT (P is the pin's momentum, T is the time it takes for the pin to go from velocity Vmax to 0, transferring all it's energy into the gun and the bullet, but as I said, let us assume all of it goes into the bullet), or F=M*dV/dT (M, mass of the pin, dV is the difference in velocity, Vmax-0, which is simply Vmax. This is because P=M*V, which means dP=M*dV, ignoring relativity). So, F=M*C/dT*sqrt(N). The time varies slightly, but insignificantly, so let us assume it is a constant. So that's it. The force exerted by the pin on the bullet is some constant (calculatable, as mentioned and as shown), times the sqrt of N, the number of rubber bands on the gun. So there you go. Just a little something I did out of the blue the other day and thought I would share a proof of my conjecture from what feels like eons ago. I hope you enjoyed. Finally, I would like to tell you guys, perhaps as a little tease, since I'm not sure if I will ever upload it, but I have made 1 more gun after I stopped posting. I have already slightly teased about it in my user info. I guess I'll tell you guys what it is if I'm already posting something here again :) Possibly my most enjoyable, most well received, and quite innovative gun of all time? The REMPAR-2. I built the REMPAR-3 (I was also going to call it S5 when I thought about posting it). In a brief summary, it's a pump action, chambering (or bolt action as I and many others falsely used to call it), magazine fed rifle, that's only 5 layers thick all over, except one tiny area where it's 8 layers thick (1.5 extra on either side), as a reinforcement, not necessary if you use less rubber bands. Oh, actually, there's another small necessary area where it's 7 layers thick, but it's tiny and doesn't make the gun look bulky at all, and who cares. Plus, the one is around the pump, which looks quite natural, and the other is "disguised" as a detachable sight (not really detachable) that also looks fine. It also looked fairly good for a gun that I made, it used (if I remember correctly) a grand total of 0 broken pieces, which is a big accomplishment for me (the mag has some broken white rods, but fuck off), and it worked flawlessly, reaching ranges over 80ft and being able to go at 2-4 rounds per second, depending on your skill level with it. In other words, I could shoot 4rps; My girlfriend, with no experience or practice, could do 2rps, which says something about the gun's comfortability and ease of use in my opinion. It shot blue rods up to an accuracy of about 5x5cm (2x2in) over 30ft, which is amazing for a Knex gun, and it was truly super comfortable. It wasn't even long at all, which is saying a lot, looking at some other people's attempts at 5-wide pump actions (I may also be guilty of an attempt several years ago). Being quite short and only 5 wide, it is also quite light. I'm sorry, I just really liked this gun, I think it was truly my best creation ever (of course, the S3 is by far the most innovative gun I've made, but it's mostly a concept gun, not meant for real effectiveness). I may post it in the future, but I'll make no promises. I suppose I won't leave you guys completely hanging and take a picture of it. Oh yes, there's also a neat, fun little thing I did, originally because I saw no other option, but then I actually really loved it. I'm talking about the mag-lock. It locks automatically (there's a band on it, but it ripped a long time ago, so...) and the mag cannot fall out. Then you pull on it with your middle finger, similar to a trigger, and the mag just drops right out. Love it :)

Topic by Sharir1701   |  last reply


BAATCH code - Math Problem?

Heey! I wanna make a .BAT program that'll help me do homework. I'm lazy to type the same formula to calculator, so I wanna make a program with preset formula. I wanna make the program solve this formula: S=3,14*r2 and O=3,14*d - Surface and Circuit of a cirle (I'm not english, my english's not the best). I wanna make the program solve these formulas. When you type r=3, it will say CIRCUIT IS (r*2 and then 3,14*'the r*2') AND SURFACE IS (3,14*r2 - the 2 should be in upper right corner) When you type d=3, it will say CIRCUIT IS (3,14*d) and SIZE IS (d:2 and then 3,14*'d:2 answer'2 - again, 2 in upper right corner. Please.......

Question by NicoFilippo   |  last reply


what are some math problems to make a efficient circuit? Answered

I am trying to make my own wind mill using a stepper motor, capacitor,led, and a resister. My problem is that my dad wants me to make it more efficient meaning making the led go brighter and longer. I curently have 11 capacitors in parallel ,one resister. what are some math equations i can use to find out how to make this more efficient and how do i use the problems? 

Question by lookwhatjoeysmaking   |  last reply


7/4 x 16/14?

Using cancelling

Question by kcardenas   |  last reply


3 1/6-1 1/3=? Answered

Question by keniad32   |  last reply


What is 1 / 0 ? Answered

Here is tricky one try and answer it... 

Question by PREDATOR_UK   |  last reply



Simplify: a2 - a - 12 a2 - 16?

Simplify: a2-a-12 a2-16

Question by Big Stee   |  last reply


multiply -7 (2a square minus 4) how do i work the problem?

Im doing basic concepts in algebra and i need to how to solve this pronlem

Question by toinette0823   |  last reply


how do i factor the polynomial x^4-2x^2 1-a^2 by grouping?

How do i factor the polynomial x^4-2x^2 1-a^2 by grouping?

Question by amythibodeaux1   |  last reply


-1 5/6 5 1/3?

I need the answer to this! I CANNOT FIND IT. It's probably right in front of my face, and I'm just stupid. Please help! its a mixed fraction. -1 5/6 + 5 1/3

Question by paigeyb   |  last reply


How to Measure From a Picture

I am trying to make a table from a picture in a magazine, which has some intricate lathe work that I want to duplicate. The problem is the picture was taken at an unknown angle, and when I try to scale up from the picture my measurements come out screwed up. Is there something I can do that we allow me to find the right measurements?

Topic by Sedgewick17   |  last reply


A Third Math Sign - not just positive or negative

I was thinking about a random thing the other week. We have positive and negative signs in widespread and ubiquitous use in mathematics. What if we had a third sign? The number line would look like the one in the picture. It's not even a line anymore. Since I am absolutely dumbfounded as to how even the basic operations would play out in this type of system (although I have a rough idea for addition and subtraction), and nor do I know what the possible applications for a redundant sign could be, I'm just putting this here. Got ideas? Fire away.

Topic by nutsandbolts_64   |  last reply


How can I put symbols or math formulas in the answer box? Answered

I was trying to answer a question earlier and wanted to put in the formula for figuring the surface area of a sphere.  Short of adding an image, I couldn't figure out how, so I just wrote out the formula. Is there a way to insert math symbols in the answer box?

Question by Burf   |  last reply


What math process is indicated by a symbol of an integral with a circle drawn at near the center of the integral symbol? Answered

I believe that this is has something to do with physics, possibly calculations pertaining to WORK. I know what an integral is but I am not sure what this is telling me to do. Derive an integral in some fashion other than standard? As I said above the symbol is a standard integral symbol from calculus except there is a circle at the center of the symbol.

Question by jc38654   |  last reply


a word of caution

Don't drink and derive

Topic by corey_caffeine   |  last reply




Statistics help, anyone?

I want to calculate a statistic involving several different factors, but don't know the math. This person has different characteristics I wish to consider.  One occurs in about 10% of the general population, one in about 15% of the general population and one in about 7% of the general population, with no relationship between the three.  In other words, one is not more likely to be found in one of the other two groups by virtue of being in the third. In a population of 34,000,000, how many such individuals are likely to occur? Thanks much

Topic by ourmoneypit   |  last reply



If 12months=100% what percent of a year is one month? Answered

12=100%, 6=50%, 3=25%, so what percentage of a year is one month? This is just for fun really.

Question by Aerospaced   |  last reply


How does one make a liquid plastic dip?

It is no longer sold in craft stores except in England and Europe. It was used to make plastic flowers. Dip in a wire form and it makes a minimum surface like a soap bubble.

Question by Kilix   |  last reply


Why "Vortex" for Vortex math and devices?

If you are new to the topic then it might give you a slightly quicker understanding than watching hours of youtube videos.I assume you have seen these various coils that make a sphere shaped magnet spin at insane speeds.They are a good start.You see by normal understanding these Rodin or Vortex coils should not be able to produce a field that rotates that fast.As with a lot of things we tried to use math to explain it in theory and than adjusted the math to match it.Vortex math was born.So how do you explain blue and red to a blind person that never saw anything?I mean in a way they actually know how it would look if they could see?Doesn't work, but we can use a Dyson vacuum cleaner ;)A lot of "tornados" add up to one giant super tornado.Spinning so fast that "all" the dirst stays behind and only clean air comes out.As in nature all the weather cells add up to one that is more powerful than the combined single ones.The tornados that form the term vortex are around the coils.But also around the entire donut as well as every single strand of wire.In any good vortex the rotational speed increases towards the center and bottom of the vortex.You can try that with some floating stuff when you drain your bathtub or sink.Try to imagine and endless tornado that runs around every wire like a spiral.The coil itself adds another spin vector to it and increases the moving speed or the single tornado.Combined it adds up to a very strong tornadoe moving very fast around in the coil pack.As this also creates a rotating field like another tornado in the donut shape it all gets twisted up.Physics as we know it won't fully explain these effects.Vortex devices that produce electricity are usually coils in a special winding configuration and pattern.Like we try to eliminate certain things with basket coils in the HF area a Rodin or Vortex coil tries to utlise these otherwise unwanted stray effects and interferences.Overunity is another term people like to use here but I leave it up to you if such a things is phsically possible with an electrical system.Vortex math tries to explain all these things demonstrated in experiments.However I found two slight flaws in the common approch.1. Only two dimension used.Unlike the coils the simplified Vortex math only operates in two dimensions.A circle instead of a sphere if you like.2. Again, unlike the coil harmony and resonance are neglected.It seems in some cases people try to draw a circle just with straight lines.While in reality you have a never ending, resonant "stream" in three or to be precise four dimensions.Is it the chicken and egg problem?Yes and no.You can only calculate something if you can fully understand it or exactly replicate it in reality.Vortex coils are just way to interpret theories and get some sort of results.And those results are the real problem.We can measure magnatic fields in strenght and direction even frequency.However we can neither make them visible in real time not measure mixed or entangled fields properly.We "see" Mars is our "red planet" but in reality it just the atmosphere, the surface is not red at all in most places.NASA has enough problems to calculated missions to outer space with enough accuracy.Just imagine they would have to do it while considering that around every path our planets make is another spinning "distraction"....That is exactly what Vortex math tries to do while eliminating common math bit by bit.You can see and hear in 3 dimensions.Maybe you are also good in drawing something in 3D on your compterscreen or 3D headset.But how many here could predict the path of a baseball in 3D like they do when watching a game?Depending on your viewing angle you might be way off....Try to know or calculate where exactly the ball is at any given monet in time and how fast it spins in which direction.....Our brains are not trained to think like this!Even if we construct things like a dome we prefer to have straight features.Sure manufacturing is one thing that needs to be affordable.But try to just calculate the support structure if all is actually fully round like a sphere should be.We avoid what is considered higher dimensions as much we can.To calculate a distance in 3D it still seems easier to use two 2D models to add up instead of true vectors.Again only through technology like computer we are able to simulate, understand and actually calculate what we need.Where we ventured around the globe and into our solar system our math was left behind.Finding workaround and good enough approximations still seems the way to go.Instead actually evolving our math to our needs we just add more and more complex formulas and calculations.To fully understand vortex math you need to let go and start thinking in 4 dimensions instead of just 2.Oh, sorry, you might be new to this...Number 4 is time of course.

Topic by Downunder35m 


Need Geometry Help!!!!!! VERY Urgent!

My school thought it would be a good idea to give me 3 massive projects all due in teh same date (2 days) I finished an enlgish project that involved a table with 300 words and theire meanings and stuff.Now I'm down to a geometry project, using the Pythagorean theorem (did I spell that right?). The problem is such:In the triangle ABC, rectangle in C (C=90 o). a=15 units and c=17 units. Unit=1/2 centimeterUse the theorem to find the third side.Well, Im a bit stumped, could anyone help me here? At least how to start it. (As far as i know, the Pythagorean theorem states that a2 = b2 + c2)help!

Topic by Keith-Kid   |  last reply


How can I add a math formula (created with a math editor) in the text of an Instructable?

I just want to include some formulas in my text, I've tried to edit it with a math editor, save it as a pic and paste  it in the text but in the preview disappears.Thanks Massimo

Question by MassimoF11   |  last reply


I got my math quiz back...

Yes I know I have horrible handwriting... But I think 1000% on a quiz cancels that out. I actuallt got a 50/50 but im not complaining...

Topic by astrozombies138   |  last reply


Help with capacitor basics? (the math part) [ANSWERED. Come here for the proof if you want it!] Answered

I understand the operation for capacitors, which make a lot of intuitive sense to me, and seems deceptively simple. I know that the derivative  of the voltage across a capacitor (the slew rate, if you will) is proportional to the current, for a given capacitance. So when the voltage is not changing much, like when it is connected across power supply rails, and the capacitor has little-to-no current flowing through it, and it appears as a high impedance. Fair enough. And when I am winding up the wick on the constant-voltage power supply, so that the slew rate is constant, and the voltage is changing at a constant rate, the current will be relative to how fast that voltage rising/falling. Again, that makes sense. I have proven that to myself time and time again. The technical math way of showing all that is this:          dV/dT * C = I or with units plugged in: d(volts)/d(seconds) * Farads = Amps (or something like that)   Likewise, I know that I can do things in reverse, and that forcing a controlled current through the capacitor, that the slew rate of the voltage across the capacitor will be proportional to that. In other words; the voltage will be integrated over time (as it steadily rises or falls). I do not like integrals in math (esp. when they require by parts or partial fractions!), but the concepts do come in handy in practical design! This is also my 2nd favorite way of imagining what an integral are! (My favorite is actually the water cup or well analogy, where a water faucet or hose is a function, and a the level of water in the cup, pool, well, etc. is the integrated result. That makes the function of integrals really clear and deceptively easy LOL!) So, I basicly have been trying to figure out how to take these simple, easy-to-understand relationships, and take ohms law, and have a super basic RC circuit, with 5V, 5 ohms, and 0.1F. I have so far figured out how to take ohms law, substitute I in the capacitor formula, and get a function. HOWEVER, this is where I get stuck. -------------------------------------------------------------------------------------------------------- Here is the circuit:            +5V---(V2)-----/\/\/\/\/\/----(V1)-----| |-------0v----(grd) So after having a bit of a think, I have figured out that I really need to account for 2 different V's. The 5V power supply, V2, and the voltage across the capacitor, V2. I know that the current flowing through everything in a series circuit is the same, so then I can easily figure out current by calculating the voltage drop across the resistor which is this:            I = (V2 - V1) / R  So now, lets plug that into the mysterious capacitor derivative thingy: (All I did was substitute the I in the capacitor formula with the that ohms law formula above.)           dV(1)/dT * C = (V(2) - V(1) ) / R. -------------------------------------------------- Now, I just plug in the values, and simplify as much as I can, to make it more friendly to my eyes. C = 0.1F, and R = 5 in my case, since I am using a 5 ohm resistor, 100mF capacitor, and I know V2 = 5V, since that is the output of a 7805 voltage reg.           d(V(1))/dT * 0.1F = (5V - V(1) ) / 5ohms. That dV/dT is a bit hard to look at, so I will use V prime, or V' to represent that instead:          V(1)' * 0.1 = (5 - V(1)) / 5 I do not know how to simplify that further though, to end up with that weird inverse exponential curve that is the time constant thingy, with that decaying charging curve. I have V on one side, and V' on the other side. :( So this is how far I got:        5 + (1/2 * V(1)') = V(1) EDIT: I HAVE ADDED THE PROOF HERE IF YOU WANT IT

Question by -max-   |  last reply


What is distinct square? Answered

Give me a description of what a distinct square is in geometry

Question by Xixfas   |  last reply


Creative ways to stay sharp on you algrebra and pre calculus skills when you're not in class? Answered

Hey, guys! Any other math enthusiast out there? I just took pre-calc with Trig last spring. My intention was to take Calc 1 this fall while pre-calc was still fresh on my mind. Unfortunately, things aren't going to work out that way. Does anyone have a really creative and fun way to stay sharp on their maths? I already have a few of my own but I want to know what other ideas people have. Thanks:) PS: My current method is solving TED riddles using systems of equations.

Question by RampedUpDIY   |  last reply


If i have a 72 cubic inch CYLINDER that is 11 inches long, what is diamater of this cylinder?

If i have a 72 cubic inch CYLINDER that is 11 inches long, what is diamater of this cylinder?

Question by trf   |  last reply


Can you allow users to use mathjax to add nicely formatted equations?

Http://www.mathjax.org/ Users can use Latex-like formatting, such as $\sum_{i=1}^n \frac{1}{n}$. See http://math.stackexchange.com for example. Thanks, Joe

Topic by angler   |  last reply


The Self-Righting Object

The Gomboc is a "mono-monostatic" object -- a three-dimensional object that purely by dint of its geometry has only one possible way to balance upright.The challenge intrigued two scientists, Gabor Domokos and Peter Varkonyi, both of the Budapest University of Technology and Economics. They spent a few years doing the math, and it seemed as if a mono-monostatic object could, in fact, exist. They began looking to see if they could find a naturally occurring example; at one point, Domokos was so obsessed that he spent hours testing 2,000 pebbles on a beach to see if they could right themselves. (None could.)After several more years of scratching their heads, they finally hit upon a shape that looked promising. They designed it on a computer, and when it came back from the manufacturer, they nervously tipped it over, wondering if all their work would be for naught. Nope: the Gomboc performed perfectly. "It's a very nice mathematical problem because you can hold the proof in your hands, and it's quite beautiful," Varkonyi says.It's apparently similar to the shape of tortoise and beetle shells, explaining why these creatures can actually flip themselves back over.

Topic by canida   |  last reply


What happens when you induce two currents of differing wavelength on the same line? Answered

If I induce two currents of differing wavelengths on a single conductive body, say an iron pipe for example, how can I calculate what the resulting signals wavelength will be? Is it as simple as taking the root mean square of the frequency of the signals? Any ideas for calculating the voltage of the final signal? ------------------------------------------------------------------------------------------------------------------------- Example: Signal 1: 60hz at 100v Signal 2: 75hz at 100v RMS frequency sqrt(((60^2)+(75^2))/2) =  67.9153 ------------------------------------------------------------------------------------------------------------------------- Thanks  a bunch!

Question by paulcauchon   |  last reply