x Turn on thread page Beta
 You are Here: Home >< Maths

# Rates of change question watch

1. Question is confusing as I don't know what formula I should use for a cylindrical tank and it says find rate of fluid in proportion to square root of V, though I am meant to show it satisfies an equation with the square root of h?
2. (Original post by TSRforum)
Question is confusing as I don't know what formula I should use for a cylindrical tank and it says find rate of fluid in proportion to square root of V, though I am meant to show it satisfies an equation with the square root of h?
dV/dt = dV/dh dh/dt
3. (Original post by TeeEm)
dV/dt = dV/dh dh/dt
Do I use V= 1/3(pi)(r)^2(h)?
If so then dV/dt = 2/3(pi)(r)(h) x dh/dt
Then what?
Edit: h= 3v/(pi)(r^2) do I sub that into -k(h)^1/2 and put it into the equation?
4. (Original post by TSRforum)
Do I use V= 1/3(pi)(r)^2(h)?
If so then dV/dt = 2/3(pi)(r)(h) x dh/dt
Then what?
you do but note r is constant, h is varying
5. (Original post by TeeEm)
you do but note r is constant, h is varying
How does knowing that help me?
6. (Original post by TSRforum)
How does knowing that help me?
I do not understand what is the problem.
7. (Original post by TeeEm)
I do not understand what is the problem.
I'm still confused, how exactly am I satisfying dh/dt by using dv/dt?
Do I need to re-arrange v into h=3V/(pi)(r)^2 and sub that into -k(V)^1/2 which I then put into dv/dt?
8. (Original post by TSRforum)
I'm still confused, how exactly am I satisfying dh/dt by using dv/dt?
Do I need to re-arrange v into h=3V/(pi)(r)^2 and sub that into -k(V)^1/2 which I then put into dv/dt?
Are you happy with post 2?
9. (Original post by TeeEm)
Are you happy with post 2?
no, I'm still confused. I'd rather you tell me the answer as I don't have it in the book I am using
10. (Original post by TSRforum)
no, I'm still confused. I'd rather you tell me the answer as I don't have it in the book I am using
I would of course tell you the answer but some people here do not like this.
I will look into my resources to find the most similar worked example to yours if you give me 5 minutes
11. (Original post by TSRforum)
no, I'm still confused. I'd rather you tell me the answer as I don't have it in the book I am using
(Original post by TeeEm)
I would of course tell you the answer but some people here do not like this.
I will look into my resources to find the most similar worked example to yours if you give me 5 minutes
this is the closest match I can find
Hopefully this will help you with yours
All the best
Attached Images
12. ODE EXAMPLE.pdf (165.0 KB, 52 views)
13. (Original post by TeeEm)
this is the closest match I can find
Hopefully this will help you with yours
All the best
Thanks! I'm assuming you can only do v = Ah instead of 1/3(pi)(r)^2h in "show that" type questions or can you use it in other rate of change questions?
14. (Original post by TSRforum)
Thanks! I'm assuming you can only do v = Ah instead of 1/3(pi)(r)^2h in "show that" type questions or can you use it in other rate of change questions?
in your question you have V = 1/3(pi)r2h
but your dV/dh = 1/3(pi)r2 = constant which you can absorb into k
15. (Original post by TeeEm)
in your question you have V = 1/3(pi)r2h
but your dV/dh = 1/3(pi)r2 = constant which you can absorb into k
Oh ok, also what about this question? There's way too little info for me to reach an answer. Is my working out wrong?

Turn on thread page Beta
TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: January 14, 2016
Today on TSR

### Loughborough better than Cambridge

Loughborough at number one

Poll
Useful resources

## Make your revision easier

### Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here

### How to use LaTex

Writing equations the easy way

### Study habits of A* students

Top tips from students who have already aced their exams

Can you help? Study help unanswered threads

## Groups associated with this forum:

View associated groups

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE