Equilibrium statistics of an inelastically bouncing ball, subject to   gravity and a random force
  We consider a particle moving on the half line $x>0$ and subject to a constant force in the $-x$ direction plus a delta-correlated random force. At $x=0$ the particle is reflected inelastically. The velocities just after and before reflection satisfy $v_f=-rv_i$, where $r$ is the coefficient of restitution. This simple model is of interest in connection with studies of driven granular matter in a gravitational field. With an exact analytical approach and simulations we study the steady state distribution function $P(x,v)$. 
Theodore W. Burkhardt and Stanislav N. Kotsev