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Homework Help: Impulsive force during collision between solid and liquid

  1. Jun 29, 2009 #1
    1. The problem statement, all variables and given/known data

    I am trying to model an impact between a solid and a liquid as a 1D elastic collision where KE and momentum are conserved. Calculating the impulse is no problem. My problem in when I try to come up with an accurate collision time in order to calculate impulsive forces. Does anyone know of a reasonably accurate approach to find these forces.

    2. Relevant equations

    Conservation of KE, Conservation of Momentum, Herztian correlations for impacting solids, elastic coefficients of impacted materials.

    3. The attempt at a solution

    Use Hertzian correlations between two elastic solids to get an idea of the impact time (around .003s) for my initial conditions.
  2. jcsd
  3. Jul 1, 2009 #2


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    Homework Helper

    Why do you think that it is reasonable to model a solid-liquid collision as elastic? Usually, such a collision is quite inelastic, since the configuration of the liquid doesn't even restore untill many collision timescales later (e.g. the ripples in the surface of a pool will continue for several seconds or minutes, even though the tennis ball only makes contact with the surface of the water for less than a second).

    The only idea that I have to theoretically determine the collision force is to consider bouyancy. However, I would expect that surface effects are also significant (e.g. surface tension), but I don't know how to deal with that.
  4. Jul 2, 2009 #3
    I modelled the collision as elastic to be conservative because it would cause the maximum transfer of energy.
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