float g = 9.8;      //gravitational constant
float t = 0;        //time in seconds
float Vx = 10;       //velocity along the X axis
float Vy = 0;       //velocity along the Y axis
float x = 20;       //x coordinate of the ball's center
float y = 20;       //y coordinate of the ball's center
float diameter = 10;  //diameter of the ball
int ground = 10;    //height of the "ground" above bottom of display
float coeff = 0.9;

void setup() {
 size(900,200);
 background(0);
 framerate(60);
 ellipseMode(CENTER);

}

void draw() {

 stroke(255);
 noFill();

 line(0, height-ground, width, height-ground);

 diameter = abs(Vy);

 Vy = Vy + g*t;
 y = y + (Vy * t);

 Vx = Vx;
 x = x + (Vx * t);

 t = t + .001;

 if ( (y + diameter/2) <= (height - ground) ) {
   ellipse(x, y, diameter, diameter);
   } else {
   y = height - ground - diameter/2;
   ellipse(x,y,diameter,diameter);
   }

 if(y+diameter/2 == height-ground) {
   Vy = (-1 * Vy);
   Vy = Vy * coeff;
   }

 if (x>=width) {
   noLoop();
   }

}