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Homework Help: Get Ready For This One

  1. Jan 6, 2007 #1
    Here we go people, need some help. Here is my problem.

    *Build a device that can raise a certain volume of water to a higher elevation using only the gravitational potential energy of the water*

    +The only source of energy allowed in the movement of the water is the potential energy in the water due to the Earth's gravitational attraction and the atmoshperic pressure inherited to the test site.

    +The final resting place of the water must be 6 inches above the original resting place.

    +The original resting place for the water may not be more than 3 feet from the floor

    +Any type of mechanism is acceptable as long as there is no source of energy in the mechanism that contributes in lifting the water.

    +Transfer must be completed in 5min

    +The machine cannot be touched once water is inserted into the device.

    +The introduction of the water may unbalance the system, but the design of the system must eventually effect transfer.

    Any ideas?? Or have you done this before? I was thinking syphon? I'm not to sure. There must be an easy way! THERE MUST BE! Thnx :biggrin:
  2. jcsd
  3. Jan 6, 2007 #2
    Let me get this straight, you want to lift water up without inputting any energy - hmmmm, sounds like that could be quite tricky to say the least!
  4. Jan 6, 2007 #3
    Yeah i know. It is very possible my Engineering Teacher says. Our whole class got this assignment and the assignment is individual. I have no clue how to do it. Maybe Hydraulics? Pressure? Energy Transfer? Mechanical Advantage? Gravity? Im allowed to use these techniques. Also one more thing. I can't spend more than $25 dollars. :biggrin:
  5. Jan 6, 2007 #4


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    Is that the whole set of instructions? Can you use the gravitational potential energy of all of the water to elevate a portion of the water? That may be do-able, but I can see no way to elevate all the water without mechanical input.
  6. Jan 6, 2007 #5
    have you thought about capillary forces from an open tube? Trees have no problem transporting water and as far as i know capillary forces start the whole process off.
  7. Jan 6, 2007 #6
    Also any rubber like vessel with the air squeezed out will only draw water in/up due to the force of the atmospheric pressure pushing down on the surface of the water (same principle as a drinking straw). atmospheric pressure supports a coloumn of water 10m high at sea level, some thingsto think about. Good luck.
  8. Jan 6, 2007 #7


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    I've got a way that this can be done without using capillary action. It requires a material that can absorb water and remain rigid enough to act as a cantilever and pivot when it has absorbed enough water. Perhaps a thin-walled plastic tube full of cotton. That's enough hints. You should be able to come back with a description of the system with that head-start.
  9. Jan 6, 2007 #8


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    Seems like one way would be to have main bucket 3 feet off the floor, and a pipe down to another bucket on the floor. Capture the energy of the water running down the pipe (however) and use that energy to pump a small amount of water up to a small cup 6" above the main bucket.

    Not sure what the most practical mechanisms would be, though. If you can make 12V somehow from the falling water, you could use a tiny electric water pump...

    Oh, scratch all that. I got a better way. Think of a water wheel, with big buckets and small buckets. The big buckets are filled by the main water reservior 3' off the ground, and that turns the wheel which dumps the water into the floor reservoir. Except you also have little buckets next to the big ones (or incompletely emptying buckets), and those get emptied by some simple mechanism at the top of the wheel. With some calculations, you could figure out the most efficient way to pump the water up to the higher elevation, using as little extra water as possible. Yeah, a water wheel! I'm going to go make me one in the garage now...
  10. Jan 6, 2007 #9
    Those are not the full instructions. Some of your guys ideas seem possible but there was one direction that daunts me. "To start the system, water will be introduced to the system. THE MACHINE MAY NOT BE TOUCHED AFTER THE WATER HAS BEEN INTRODUCED TO ACTIVATE THE SYSTEM, WITH THE EXCEPTION OF TURNING ON OR OFF A VALVE" I've been thinking about this project all day and still have no design that follows all the restrictions. Iv'e never been so stumped in my life. I was thinking about that wheel tho...
  11. Jan 6, 2007 #10


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    This is an elementary problem with a bit of practical engineering overlain. Don't over-think this one. If you come up with a reasonable solution based on my previous post, I will help you refine it.
  12. Jan 9, 2007 #11
    AS water is poured into a sealed container so long as the air can't escape (use a valve) then water should be forced through any other exit point (all under pressure inherent to the system ie, not altered by external forces other than the addition of water). a tube and raised container to collect the forced out water. (depends on wether the change in pressure is allowed)
  13. Jan 10, 2007 #12


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    Has anyone heard about impulse pumps?

    Have I said too much? :smile:
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