suprabeast

need to solve a first order differential equation so that i can then draw an estimated response and i'm a bit stuck


dx/dt + 3x/2 + 1/2 = 0

where x(0) = 1/3

anyone good at control theory and laplace transforms??

Big Daz

Oooo Control. Just did my degree exam on Friday for this, I will have a look if I havent forgotten it all already

Daz

Spoon

That's well easy but as Big Daz was first to respond and needs the practice, obviously, I'll let him answer.

p.s Second order differential equations, now that's a different matter, well ard them.

I bet someone puts a link up and cheats.

lightning101

http://www.math.uiuc.edu/~dcmurphy/m...estfsolns.html

suprabeast

well i gotta do the second order ones later which is scary!

i've got an answer that takes me as far as the s plane which is x' = (2s-3)/(2s^2+(3/s)).. but i dont think its right!!!

aaarrrgghhhh ! ! stress...

Mick

iTrader: (1)

Good grief, - I remember the words from ~ 12 years ago - even passed an exam in it - but I haven't got a clue what you're on about now

How time flies

Good luck

Mick

Mick

iTrader: (1)

Darn double posted trying to correct a typo before the message went...

Mick

ajm

I remember doing this in the dim and distant past... can't really remember Laplace and may be way off track but can you do it by separating the variables such that:

dx/dt = -3x/2 - 1/2

integral (1/(-3x/2 - 1/2)dx = integral(1)dt

Then integrate each side?

suprabeast

thanks i'll try that, see if it gets me any further!!

paul-s

or you could do 6 + 6 take away 10 = x + 1

Spoon

Same here, kids love going at Christmas time though

TelBoy

I remember Linda Lovelace. Does that help?

Apparition

Have the Martians landed???? whats all this gobbledegook ????

Iwan

Ditto, wouldn't have a clue now as I haven't done that sort of stuff for 10 - 12 years.

Spoon

Never takes much to confuse a female, hey Tel?

TelBoy

Absolutely. Apparition, KNOW YOUR PLACE.

ajm

It's all gone very quiet.... have you integrated it?..... or have you given up and gone out on the p!ss at the taxpayers' expense with the rest of your student brethren?

Dave1980

what is all that about?. seems pointless as unless you are going to become a science boff what the phook are you going to use it for?

ajm

Not much... just anything that requires an automatic control system!

Dave1980

well fair enough, just seems a lot of the stuff that you learn at uni you never use. I am a construction engineer and spent years at uni training.
when you come out you hardly have to use any of the formulas or whatever as there are easier ways of doing it. obviously there are exceptions but surely it cant all be relevant.

suprabeast

never got round to integrating it! and didnt even make it to the pub! Not that i can spend money at the tax payers expense either unfortunately! I work full time in an engineering firm who sponser me to go to uni, I asked when i started if they would be prepared to do it and they said yes so i figured why not!!!

So unfortunately, i pay just as much tax as the rest of you lot and get 1 day off a week! If you call 12 hours of lectures a day off!!!

Oh well, i will find the solution on thursday if i havent sussed it by then! thats my next day in!