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Homework Help: Dynamics Question (water falling from the side of a tank)

  1. Mar 28, 2008 #1
    [SOLVED] Dynamics Question (water falling from the side of a tank)

    1. The problem statement, all variables and given/known data
    A large tank rests on the ground and has a water level 10 m above the ground. Water issues from a small hole in the side, 1 m below the the surface of the water. How far from the side of the tank will the water hit the ground ? Is there another height at which if a hole were drilled there, the water from it would reach the ground at the same point? Justify ur answer.

    3. The attempt at a solution
    as every logical person i assumed that water falls in projectile manner so on the x -axis you have x = v(x)t where x is the position where the water hits the ground, v(x) is the x-component of velocity and t is time; on the y axis you have accelerated motion and so you have 2 eqns :

    y = y0 + 1/2 gt^2 and t = v(y)/g

    where v(y) is the y - component of velocity, y is the height, and y0 is the starting point.

    i found the time t from here but i fail to go any further because i don't know how to get v(x) or sth that can help me find v(x).

    Now this might not seem like an undergraduate problem but i am in 2nd yr and we are having sth like a general physics paper as a revision kinda thing. so this is in reality 1st yr dynamics staff. And its weird that i can't solved it because i used to be good in these. *sigh*
  2. jcsd
  3. Mar 28, 2008 #2

    Doc Al

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    Staff: Mentor

    Assume that the water issues from the hole horizontally.

    Hints: Find the initial speed as a function of hole height (h). Then try to find the horizontal distance as a function of h.
  4. Mar 28, 2008 #3


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    Science Advisor
    Homework Helper

    Welcome to PF!

    Hi CloudDreamer7! Welcome to PF! :smile:

    It can't make any difference whether there's a great big tank or just a curved pipe which finishes horizontally and which happens to be 1m from top to horizontal outlet.

    In steady flow, I think it doesn't make any difference whether the water comes continuously, or comes in "bullets".

    So work out the kinetic energy for a bullet of water falling 1m. :smile:
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