  We show that in complete agreement with classical mechanics, the dynamics of
any quantum mechanical wave packet in a linear gravitational potential involves
the gravitational and the inertial mass only as their ratio. In contrast, the
spatial modulation of the corresponding energy wave function is determined by
the third root of the product of the two masses. Moreover, the discrete energy
spectrum of a particle constrained in its motion by a linear gravitational
potential and an infinitely steep wall depends on the inertial as well as the
gravitational mass with different fractional powers. This feature might open a
new avenue in quantum tests of the universality of free fall.
