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Force of water running through a hose

  1. Jan 1, 2014 #1
    My daughter is doing a science experiment based on a launch loop (http://en.wikipedia.org/wiki/Launch_loop).

    I hooked a 2600 psi pressure washer to two 1/8" OD tubes and then tethered them to a board. We rolled a tennis ball over the top of it when the water was flowing through the tubes (not just pressurized, but blasting out the end), but the tubes are not rigid when the water does not flow.

    I understand the basics of the forces involved, but I don't know the details and have know idea how we can predict its performance. Can anyone help or point us in the right direction?

  2. jcsd
  3. Jan 1, 2014 #2


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    Gold Member

    Well OK. that's neat. Never heard of that before as a way to launch vehicles into space.

    Anyways, when something is moving it will do so in a straight line. If a force now acts sideways on, or tangent to the velocity of, this moving object then the trajectory of the object will change, and it will follow an arc of a circle if the force is constant.

    The water from the pressure washer is the object, even if it is continious stream, but one can look upon it as a series of objects following one right after the other. The sideways force is providfed by the hose, which then takes up the form of an arc. The arc shape of the hose probably may not be a part of a circle, since the sideways force may not be constant, but vary along the length.

    You should know, or maybe not, that anything rotating about a central axis has a centripital force acting on it.
    Such would be a ball attached to a string swung around your head where the tension in the string provides the inwards force. Or a planet moving around the sun, where gravity provides the force.

    Your scenario is most likely a bit more complicated.

    as a start,
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