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Calculating angle of thrown sand

  1. Dec 22, 2012 #1

    I would like to calculate the angle and distance sand will travel after it has been impacted by a rotating object such as a rotating brush (like those street sweepers).

    Example if were to take a spinning bike tire (ignore tread) and spin it up to let's say 100 RPM and lowered it until it made contact with the sand. How could i determine the angle (most important) the sand will be thrown upwards and the distance it will travel.

    My Problem
    I have a system that sweeps sand up into a bucket. My problem is that a lot of the sand goes up and falls back into the brush system instead of going at an angle of let's say 135° into the bucket.

    This picture shows my setup. The red arrow is the angle I must achieve to get the majority of the sand in the bucket.

    Attached Files:

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  2. jcsd
  3. Dec 22, 2012 #2


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    Staff: Mentor

    It will depend on many parameters of the sand and the geometry of the setup.
    As rough approximation, you could assume that the sand gets the same velocity as the lower tip of the brush, and performs an inelastic collision once it reaches the incline. If the remaining kinetic energy is enough to reach the top of the incline, it might work. In addition, I would add some safety margin to account for friction and so on, and test it.
  4. Dec 22, 2012 #3


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    Gold Member

    It looks like your bucket is closed.
    Perhaps ventilate it for air to move up the incline along with the sand.
    As mfb says, the parameters are too numerous to give a qualified answer.
    You could test rpm, radius of brush, length of incline, wetness of the sand, grain size of sand, stickiness of brush bristles and sand, depth of travel of bristles into sand, etc....
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