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Pressure of Falling Sand

  1. Feb 9, 2009 #1
    1. The problem statement, all variables and given/known data

    Grains of sand of mass 2.90x10^-3 g each, fall from a height of 0.5 m on a sticky surface at a rate of 45 grains per second per cm^2. What pressure does this shower of sand exert on the surface, assuming that air resistance can be neglected?

    2. Relevant equations


    3. The attempt at a solution
    I don't know where to start. Anyone care to point me in the right direction?
  2. jcsd
  3. Feb 9, 2009 #2
    You can work out the velocity with which every grain of sand lands. You also know what total mass of sand falls per second. Your force, [itex]F[/itex], is equal to the force required to accelerate that certain mass of sand by that certain velocity in one second.
  4. Feb 9, 2009 #3


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    Welcome to PF :smile:

    P = F / A is definitely useful here.

    Also of use is

    F = Δp / Δt

    where little p is momentum (not pressure). You'll need to figure out the change in momentum, for the total of all grains of sand that hit a square cm of the surface, in 1 second.
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