First of all, the clock moves from 0 to 1, so the code you posted will meet
problems.
If you want something to move quickly at first then slowly, say:
translate <0,-sqrt(clock),0> //think how y=sqrt(x) varies from 0
to 1
If you want something to move slowly at first then speed up, say:
translate <0,-sqr(clock),0> //think how y=sqr(x) varies from 0 to
1
