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A horizontal tube of radius $1\ \mathrm{mm}$ and length $40 \ \mathrm{cm}$ is connected to the bottom of a cubical tank of sides $100\ \mathrm{cm}$ containing water of viscosity $0.01 \ \mathrm{poise}$ . From the full tank, water is allowed to flow through the tube. Determine the time in which the tank will be half full.

My Attempt: Using Poiseuille's equation we get : $$ V=\frac{\pi P a^4}{8 \eta l} $$ where $V=$ total volume that passes through the tube per unit time.

$P=$ the pressure difference between the two sides of the tube,

$a,l$ are the radius and the length of the tube respectively and $\eta$ is the coeff. of viscocity of the liquid.

But here $P$ is a function of time. So I couldn't find it as a function of time.

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  • $\begingroup$ See this post on asking homework questions. Physics.SE is not a place for people to do your homework for you. You should ask about particular concepts you are having trouble with. You should also include what you do understand about the situation, what you have already tried, and where in particular you are stuck. $\endgroup$ – DilithiumMatrix Nov 27 '15 at 5:37
  • $\begingroup$ I know all that, If you can solve it, give the answer, if can't then please don't give me suggestions like that. $\endgroup$ – Sahil Nov 27 '15 at 8:57
  • $\begingroup$ I've explained why this question is being closed, and what you can do to get someone to actually help you solve this problem. $\endgroup$ – DilithiumMatrix Nov 27 '15 at 18:25
  • $\begingroup$ And you think there is no particular concept in that question? I explained what i tried, and in what point I faced trouble. What's the problem? $\endgroup$ – Sahil Nov 27 '15 at 20:08