Calculate Speed of Water Ejected from Hose

[dvyu]

It takes 30.0s to fill a 2.00-L container with water from a hose with a constant radius 1.00cm. The hose is held horizontally. Determine the speed of the water being ejected from the hose.

I have attempted this question, but I have got a different answer to my textbook. I may however be going about this the wrong way.

Attempt:
4p(0.01)/30^2 = 2pV/30
V = 2.09E-3 m/s

 

[radou]

What exactly does your attempt represent?

How is the flow defined and how can you calculate it from the given data? Further on, how does the flow relate to the area and speed?

 

[dvyu]

oh yes - I was using acceleration formulae
So, I should be using
area = flow/velocity and flow = Litre/second

 

[radou]

oh yes - I was using acceleration formulae
So, I should be using
area = flow/velocity and flow = Litre/second

Try to do so.

 

[dvyu]

I have used that formula -
velocity = (2/30)/(3.14*0.01^2) = 212.2m/s
The thing is, my textbook gives the answer as 21.2cm/s, and my answer converts to 2.12cm/s. Am I wrong or is the textbook wrong?

 

[radou]

Your answer is wrong.

 

[dvyu]

Okay - can you tell me where I went wrong, because I can't see where I went wrong

 

[radou]

Okay - can you tell me where I went wrong, because I can't see where I went wrong

You went wrong with the flow units. 1 [L] = 1 [dm^3]. Convert to [cm^3].

 

[dvyu]

okay, thanks, I'll try again

~it's worked out, thanks for your help

 

[2much]

Sorry, a better question is why is area equal to flow / velocity and since 1 L equals 1dm wouldn't 1L equal to 10cm? So than why do we have r as 0.1?
velocity = (2/30)/(3.14*0.01^2) = 212.2m/s

Oh i see you are converting 1cm into dm. I still can't grasp how area = flow / velocity?