Aaaaah.. Excuse me, now I've tested the code and found what's wrong. Try this one
rem Make a ball and something to bounce on
make object plain 2,100,100
xrotate object 2,90
make object sphere 1,20
rem Position them
position object 1,50,100,50
position object 2,50,0,50
rem Set manual synchronization on
sync on
rem Set ball bounsing power
pow#=2.0
rem Start loop
do
rem Increase gravity
grav#=grav#+0.05
rem Position ball at new location
position object 1,50,(object position y(1)+pow#)-grav#,50
rem If ball touches ground then reset gravity to zero
if object collision(1,2) then grav#=0
rem Point camera at ball
point camera object position x(1),object position y(1),object position z(1)
rem Update screen
sync
loop
I didn't steal it!