Exponential Decay / Finding Half Life

[abdulrahman226]

Also, when I calculated it, 10+20+40+80+160+320+640=1270 and ur answer is 1280

do I have a mistake in calculating??

[duckhero3]

@patrickJMT so does this meam i shouls solve it like 0.5a=ae^8.56t and then tjat would be ln0.5/ln8.56?

[duckhero3]

hello this vid helped me super mucho but have a conflicting issue on how to connect that into this problem: radioactive iodine decays accorindg to the equation y=ae^-0.0856t where t=days...how should i find the half life here? is the percentage decay 8.56%? nd then go from there likeyour vid?

[patrickJMT]

@duckhero3 let a = some amount, let y = half of that amount, solve for t.

[wen2669]

please dont say LN please say natural log. it encourages us to use college math words

[patrickJMT]

@wen2669 lol

[samjenkinssam]

love the video man

[sprattysy]

good work here

[HouseMDlover]

thanks pat

[shellybirdy]

really informative and interesting

[ZacIsBr00tal]

really helped me study for my exam! Thanks

[clararourk]

thanks so much my math teacher told us to learn and research this ahead so i know what we are going to be talking about tomorrow!

[xXArmyofOne1Xx]

I have a question. My pre-calc teacher never really taught us logs and ln so I'm now I calc and lost beyond belief. Your example helped but what else is out there?

[PearlBaby76]

May the Lord bless you many times over, 2 teachers (Chem n calculus) tried 2 teach this 2 me n I was lost... less than 7 mins with you and it all makes sense.

[lmaominh]

Today i was humiliated by my teacher because i didn't know how to do this. he never taught it. the overachievers of course, knew everything before he even "teaches." he also made fun of my name... it was horrible. NOW i understand what we're doing... Thanks PatrickJMT!

[patrickJMT]

@lmaominh sorry to hear that. my 8th grade science teacher, mr cox (now there is a name you can make fun of) told me i was a nerd cause i knew the answer to one of his questions. lots of weird people out there, teachers included.

[VerifiablyNoticible]

trying to look up half life related tutorials on youtube = searching through endless videos of Half Life (The video game...)

[patrickJMT]

@VerifiablyNoticible put a math term in the search as well next time : )

[joeydoit1423]

@VerifiablyNoticible add differential in your search. it is a differential based equation.

[Iamorton]

our generation have it way too easy too learn but its easier to be distractied on the internet

[MechInvent]

thanks youtube, for teaching me more than college does

[patrickJMT]

@MechInvent my name is not youtube

[ian559fresno]

@patrickJMT its okay people call me fresno lol

[psychoanalyst]

you're awesome!

[thexkiller5]

I love you!

[Yukiseim]

So just wondering, what is the difference between this formula that you teach, and A = Pe^rt? Are they the same? Or if not, under what circumstances would you use each equation? Thanks for the help!

[user7512]

Hey Patrick. Do you have any videos on continuous growth/decay rate. I am learning exponential growth and decay but with the formula, y(t)=y0e^kt (y0 = y sub 0)

Thanks a lot! if only my math teacher were as good as you!!!!

[xXREDIDSNPRXx]

Can't you just use 0.96 @ 1:29 ?

[KittyKatCurls]

My professor is using a different process and I'm lost. She's using Qbase0 e^-kt.

She didn't explain. It's with chapter of Logarthmic Functions if that helps any. I'm assuming in later converts into the natural logarithms you have here. Is there an example you can show me for this?

Question looks like: (Find the associated exponential decay or growth model) Q=1000 when t=0 and half-life =1.

Another  Question: Find half-life or doubling time when Q=1000e^0.5t

Please help math genius!!

[patrickJMT]

@KittyKatCurls this is annual decay rate; you are using the formula for continuous decay rate

[paorarkandon]

domo arigatou gozaimashita...^_^

[NiceZack]

THANK YOU PATRICKJMT def showed me a flaw in a project i was about to hand in. Freakin life saver right here!

[smexyashleyxoxo]

Thx so much!!!

[Raider9461]

Is the method pe^rt very good? where p is the number that we start with and r is the rate and t is the years....



[alexottas]

so helpful thank you thank you

[bsrkoacar]

my teacher gave me the equation A(t)=Ao^e^kt is this the same thing?

[steepphh]

isnt the equation y=a(1/2)^t/h

[leo21081996]

you are so good !

[adhami8]

our teacher did`nt show us by log method

this seems easy but we havent studied log yet

she showed us by dividing 100 by 2 then continuing



[aka7minimouse]

you are an excellent teacher but this Half-Life method is seeming to confusing for me. my teacher shows us a chart method whree you have 3 rows in the chart. Number of half lifes/Time elasped/Amt. remaining. Do you know this method?

[patrickJMT]

@aka7minimouse it just sounds like your teacher is trying to make some systematic procedure for people to follow.

[lilmizmm]

Thank you so much! That was very helpful!

[Jmerino7]

For some reason i learn this in algebra 2. I did not know it was Calculus, either way it was a fun method to do, and play around with.

[patrickJMT]

@Jmerino7 there is no calculus in this video

[saifirefly]

@patrickJMT would there be a reason for it to not be taught until a Calculus level? because we just started this in my AP Calculus AB class

[patrickJMT]

@saifirefly well, exponentials would be taught in any algebra class

[mebramo]

is the formula always the same, i mean the only chage is the rate of change (1+r). I mean the formula of decay would be in anycase: t = ln(.5)/ln(1+r)

am i right?

[xxcowslayerxxx]

@mebramo yes you are right but only use .5 if it askf for half life, if it asks when will 70% of the material be left use .7 etc...

[mebramo]

very useful video!, im not very experienced in maths and things like this. but i have a query, do you know if for using this formula you need exponential values? what happens is you use non-exponential values? Many thanks for helping out

[Wunderscat]

Thank You for Sharing!!

[MrEveleigh11]

when i try to compute the ln(.5)/ln(.96) i get 16.8 what am i doing wrong

[kevinzawssum]

cool, now if only i could locate the ln button on my calculator, i'll be all set for exams

[jesspooks]

I'm just a little befuddled...when I plugged in ln(.5)/ln(.96), I didn't come up with -.69.... I ended up with 16.9797...I even used the log instead of ln and I got the same answer. I don't know what I'm doing wrong! Help? Please and Thanks! :)

[MsWaldorfToYou]

OMG thanks sooo much for this! I have a test on this tomorrow (exponential functions) & I got everything except half life. So end of class today my teach is like LOTS OF HALF LIFE QUESTIONS ON TEST TOMORROW!! I was like CRAP don't know any of this..& my friends aren't very smart!! :o( lol THANKS BUD YOU SAVED ME!

[sullivanseven]

Hi JMT! :)

I don't understand what is the difference between the formula A(t)=Ao.e.^-kt

If they are not different can you do some more complicated ones with your good formula. If no, can you please do some from the other formula :)

good luck

[XxMissionaryxX]

your a genius dude, you make everything so simple

[datboiy20]

thanks man your videos are helpful

[slredfern]

how did you get -.69? video time 4:50

other then that I get it, You break things down really well.

[elerfe]

@slredfern ln of 1/2 is -.69 you could check it in a calculator

[Tomoya789]

THANK YOU SO MUCH! I actually used this equation to figure out how to solve exponential decay problems for my chemistry test , you just saved my ass big time.

[collegehuman1990]

hey, I know this has nothing to do with the subject matter you just taught, but can you please help me figure out how to find the roots of this: x^5-4x^3+5x-11? I need to find five roots

[aparrotslife]

If I could be granted one wish, I would wish for PatrickJMT to teach at my school because he's a very effective teacher--very easily understood! KUDOS! :)

[Stairs3000]

you are the jesus of math.

[ian559fresno]

@Stairs3000 he's the Patrick of math.

[JolienMichielsen]

Hey Due u are the secret of my success in math

thanks

[lovethinkdream]

you saved my life. words cannot express how amazing you are!

[TheSecretDaniel]

ya Half-Life is a good game

[jfhajdsfhajdsfkjafja]

is y= a (b)^t the same as y= C(a)^x

[ohgoodlord]

because our math books are the same and they are both fucking retarded. this guy is way better and not pretentious at all.

[itrancei]

Thanks a lot! Natural logarithm rules!

[itrancei]

Oh yea! I won't be getting the A in my math class if it weren't for your videos! Thanks so much :) Keep doing what do you best xD

[ExploreYourMindNC]

awesome, thanks

[hulk23869]

Our teacher showed us a different way, but this is much easier, I hope he accepts this method on the test.  Thanks, you rock and keep up the good work!

[patrickJMT]

i would ask first!

sometimes, it is about the process - not about the actual answer (well of course, the answer is important, but they are trying to teach a process in algebra class).

your instructor may be trying to emphasize something that this procedure leaves out ! (not sure what it would be, but again, i would ask to make sure)

[jfhajdsfhajdsfkjafja]

is y= a (b)^t the same as y= C(a)^x

[xnick01295]

Thank you!

[patrickJMT]

no problem mr. nick-bucket!

[xnick01295]

I just noticed...

You're a lefty!

Just like me!

Ha.

[patrickJMT]

boo ya!

i always count the number of left handed people in my classes...

[Chasesk88]

@patrickJMT im lefty also =D