The motion of the confined ball using Eqs. ~23!, ~24!, and
~27! is shown in Fig. 4. These results are for a solid sphere
(a52/5) which has a velocity across the channel such that
Dt5w/vy050.05 s. Figure 4~a! shows the velocity of the
ball along the channel both in the presence of gravity ~solid
line! and without gravity ~dashed line!