Hertz beyond belief.

@article{He2014HertzBB,
  title={Hertz beyond belief.},
  author={Andong He and John S. Wettlaufer},
  journal={Soft matter},
  year={2014},
  volume={10 13},
  pages={
          2264-9
        }
}
We examine the validity of Hertz's linear elastic theory for central collisions of spheres using a viscoelastic model. This model explains why Hertz's theory is accurate in predicting the collision time and maximum contact area even when 40% of the kinetic energy is lost due to viscous dissipation. The main reason is that both the collision time and maximum contact area have a very weak dependence on the impact velocity. Moreover, we show that colliding objects exhibit an apparent size… 
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