  We present an exact derivation of the survival probability of a randomly
accelerated particle subject to partial absorption at the origin. We determine
the persistence exponent and the amplitude associated to the decay of the
survival probability at large times. For the problem of inelastic reflection at
the origin, with coefficient of restitution $r$, we give a new derivation of
the condition for inelastic collapse, $r<r_c=e^{-\pi/\sqrt{3}}$, and determine
the persistence exponent exactly.
