unit step function. #dan815

- anonymous

unit step function. #dan815

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- anonymous

|dw:1443667583385:dw|

- anonymous

just to be clear, we can represent this as X(t)=u(t)+2u(t-1)

- dan815

you can rewrite that as a summation of some other step functions

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## More answers

- dan815

yes

- anonymous

SIK

- dan815

uhh lemem see

- anonymous

getting the hang of this

- anonymous

actual problem is this sox

- dan815

|dw:1443667664012:dw|

- dan815

yeah what u want to do is actually u(t) + u(t-1)

- anonymous

|dw:1443667692857:dw|

- anonymous

X(t)=11u(t)+12u(t-1)

- dan815

the graph is a bit confusing u want it 10 until 0?

- anonymous

10

- dan815

what u did will result in 23 at your highest step

- anonymous

has constant feed rate of 10m^3/min (theoretically) but at time t=0, a disturbance pushes 1m^3 of water into the tank and an extra 2m^3 of water at t=1min (So an additional 1m^3 of water per min)

- dan815

okay lemme get this right though u want 10 before 0?

- dan815

u know for laplace transform it cuts off the part before 0

- dan815

because if u look at the power series
summation n from 0 to inf x^n
this only converges when x<1

- dan815

|X|<1

- anonymous

yea, they draw these graphs just to show use the theoretical flow regime. yes it cuts off at 0 for laplacing, but we have questions that show graphs like these.

- anonymous

because another example, where

- dan815

okay okay lemme make sure about 1 more thing

- dan815

upto where do u want the 10 on the negative side

- dan815

forever?

- anonymous

|dw:1443668012704:dw|

- anonymous

they have function X(t)=90(u(t)-u(t-0.1))

- anonymous

so pretty much i just applied it to get X(t)=11u(t)+12u(t-1) but need confirmation

- dan815

whats the question again

- anonymous

|dw:1443668159355:dw|

- dan815

11u(t)+12u(t-1) that wont give u that

- anonymous

i just need to find this function as step function

- anonymous

so i can solve this silly problem

- dan815

lol okay ill show u best way to do this

- dan815

just draw some step functions and see how to add them

- anonymous

neeeed

- anonymous

how about 10(u(t)+2u(t-1))?

- anonymous

question is this btw for anyones interest

- anonymous

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- anonymous

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- dan815

|dw:1443668206318:dw|

- anonymous

10+u(t)+u(t-1)?

- dan815

ya that works

- anonymous

say we have this drawing again

- anonymous

|dw:1443668443342:dw|

- dan815

yep

- anonymous

they said the step function was x(t)=90(u(t)-u(t-0.1))

- dan815

that doesnt work

- anonymous

thats the answer....

- dan815

they are missing a 10

- dan815

plug in a value for t lets say t=2

- anonymous

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- anonymous

it legit has it in a book haha , omg I'm confused

- dan815

maybe they just dont want to cover the 10, what they have there is

- dan815

|dw:1443668705765:dw|

- anonymous

perhaps they just shift it down so its just normalises it

- anonymous

which really would affect the problem aye

- anonymous

wouldn't*

- anonymous

|dw:1443668833633:dw|

- anonymous

would be X(s)=10u(t)+11u(t-1)

- dan815

X(s)=10*U(t)+u(t-1)

- anonymous

why isn't it 11u(t-1)? aren't we increasing an addition m^3 after t=1min

- anonymous

ohhhhhhh

- anonymous

pellet

- dan815

lolq

- anonymous

yeah cause your steady state value is still at 10

- dan815

yes

- anonymous

and u just add a step function of magnitude 1 extra YRESSSSDQIDLFYHQBLERBFHIRL

- anonymous

DAN u da man

- dan815

i beeen telling u this lool

- anonymous

shhhhhhhhh

- anonymous

hahahahahaa

- anonymous

3weeks of lapalce transforms and its a subject inside this course, i rekn I'm doing well to grasp a lot of things haha

- anonymous

that just clicked aye

- anonymous

nigsss

- dan815

lol!

- dan815

i think laplace transforms might be a waste of time

- dan815

who knows

- dan815

its to introduce u to fourier transforms

- anonymous

lel, we use lapalce transforms in process control so its easier to solve differential equations (approximate it using linearisation)

- dan815

ye but eventually DE become too hard with laplace, so u gotta use fourier transforms for PDES

- dan815

i better get back to work T_T

- anonymous

yeah tru dat but that was for eng math. i guess we aren't looking at too hard of ODE's but i guess they teach us this smack and we have to learn their way of calculating there questions

- anonymous

yea np, peace

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