lua - How do I invert this equation? -

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i'm making simple animation ball bounces repeatedly. equation bounce h = rt / 16t^2, h height, t time in seconds, , r initial speed. problem ball bounces up-side-down. i've been playing around equation, can't right. can see wrong this?

function move_ball()   count = count + 0.3   local h = (ints*count)-(16*(math.pow(count,2)))   if (h < 0)     count = 0     move_ball()     collision()   else     ball.y = h / scale   end   if (ball.x - ball.rad < 0)     ball.dir = ball.speed     collision()   elseif (ball.x + ball.rad > length)     ball.dir = -ball.speed     collision()   end   ball.x = ball.x + ball.dir end

perhaps need like:

ball.y = height - (h / scale)

with test sure ball.y doesn't go negative.


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