how to calculate a negative acceleration?

Question

I\'m implementing the scrolling behaviour of a touch screen UI but I\'m too tired in the moment to wrap my mind around some supposedly trivial piece of math:

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Answer 1

Acceleration is the first order derivative of velocity and second order derivative of distance. Your graph looks like a second order parabola something like C-k*x^2 for some constants C and k. If y is really distance you need a=-2k, if y is velocity you need a=-2kx. In either case velocity v(x) = V0 + a(x)*x. (Where x is actually time. I am following your convention and not using t.)