rate of change (1 Viewer)

[mizz_smee]

in the 2002 HSC Q7 b
A cooler, which is initially full, is drained so that at time t seconds the volume of
water V, in litres, is given by

V=25(1-t/60)^2 for 0<t<60

i) how much water was intially in cooler?
answer - 25 litres

ii)After how many seconds was the cooler one-quarter full?
answer - t=30

iii) At what rate was the water draining out when the cooler was one quater full?

i thought i had answered the last question but i did it completly wrong according to the sucess one books and i don't understand how they got their answer i was wondering if some one could tell me how in plain english!

 

[Xayma]

dV/dt=50/60(1-t/60)
=5/6(1-t/60)
At t=30
dV/dt=5/6(1/2)
=5/12 Ls^-1

 

[mizz_smee]

how did u get 50/60
i know that it is going to be so obvious
but just tell me neway

 

[mervvyn]

it's the derivative of the expression for V

 

[mizz_smee]

i got it now
it just all of a sudden came to me
after trying to figure it out for ages
when i wasn't even really thinking about it

 

[psych_girl]

I hate rate of change. It is totally rubbish.

 

[psych_girl]

H-s-c

oh, by the way, motion is a rubbish topic too.

 

[Li0n]

as if it is, they are beautiful topics

 

[withoutaface]

as if it is, they are beautiful topics

I would put it to you that sequences and series is not.

 

[paper cup]

yes anything to do with physical applications officially sucks.

 

[~*HSC 4 life*~]

everything is good except for shitty probablility sorry justin!

 

[withoutaface]

Good doesn't even begin to describe how fabulous probability is.

 

[Emily.]

oh i love probability cos i can actually do it!!
i really need to sort my notes out and get down and do some work....

 

[Li0n]

I would put it to you that sequences and series is not.

AMEN BROTHER

 

[Li0n]

oh i love probability cos i can actually do it!!
i really need to sort my notes out and get down and do some work....

i love probability, but im not good at it :/