Translations:Development/Tutorials/Physical Simulation/61/en

The constructor sets the time step of this class and defines the acceleration constant, together with some starting conditions: we start at pixel, with zero velocity at time zero. The getPosition method returns the current position and the next time step does the calculation. If the current position and velocity are negative, the ball is hitting the floor and has to bounce back. (Omitting the velocity condition might result in a strange behavior.) Bouncing back implies a reversal of the velocity. The new velocity and position are calculated according to Newtonian mechanics. Check the corresponding Wikipedia if you like.