Minecraft wiki entry for Transportation, associated text: An exact function to calculate the speed of a (free)falling player is the following: v(t) = (392/5) ((98/100)floor(20t) - 1). Where the velocity v is in blocks/second (or meters/second), the time t is in seconds, initial velocity is zero and downward motion is negative. 20 t is floored because Minecraft updates once each tick.