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Homework Help: Help on Fluids in Motion problems

  1. Jan 2, 2005 #1
    Every second, 1.2 cubic meters of water enters a heating system through a pipe of medium width, A, with a cross sectional area of .2 meters squared. The water then flows into a wide pipe, B, with an area of .6 meters squared, and flows out through a narrow peipe, C, with an area of .1 meters squared.

    1) what is the flow rate in each pipe?

    2) what is the length of the segment of pipe A that contains 1.2 cubic meters of water? What is the length of segment B? C?

    3) How much time is required for water to travel the lengths you found in pipe A? B? C?

    4) What is the flow speed of water in each pipe?

    5) Does the speed of water increase when it enters a narrow pipe? Does the flow rate increase? Explain.
  2. jcsd
  3. Jan 2, 2005 #2


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    The idea is to post your work,not just leave the problem to somebody else to do it.

    What is the formula that u must use??Actually,there are more,but one of them is really of the domain of fluid dynamics.

  4. Jan 2, 2005 #3
    If i knew the formula that i must use, i wouldn't be asking for help on this forum. I'm just completely clueless on this one. I have no idea what formula to use or how to start. This is from a college level book and I'm only a soph.
  5. Jan 2, 2005 #4
    Well there's a volume flow rate you can use Area * velocity (Av)... There's also the mass flow rate but it doesn't seem like you need it in this question...
  6. Jan 2, 2005 #5


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    I have no idea what 'sophomore' means...Let's get back to physics.U'll need the conservation law of mass for one incompressible fluid:
    [tex] S_{1}v_{1}=S_{2}v_{2} [/tex]
    ,where 'S' stands for surface and 'v' for speed.
    This formula should get through the fourth question.

    For the first use the fact that the fluid is incompressible.The flow should be constant.

    Assume the pipes are cylindrical.At point b) you're asked about the length of the pipe,when u're given the volume and the surface.I guess this should not be too difficult.

    After finding the 3 lengths,at point c) you must compute the time the water flows through each portion of the pipe.U have computed the legths,u know the speeds,the times are easy to find.

    At point 5) u need to analyze the conservation law i stated above.

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