// Simulates the dropping of two balls from various heights.
import java.awt.*;

public class Balls {
   public final static int PANEL_HEIGHT = 600;
   public final static int PANEL_WIDTH = 600;

   public static void main(String[] args) {
      DrawingPanel panel = new DrawingPanel(PANEL_WIDTH, PANEL_HEIGHT);
      Graphics g = panel.getGraphics();
      
      int ball1x = 100, initialBall1y = 600, v01 = 25;
      int ball2x = 200, initialBall2y = 500, v02 = 15;
      
      // draw the balls at each time increment
      for (double t = 0; t <= 10.0; t += 0.1) {
         double height1 = initialBall1y - displacement(v01, 9.81, t);
         g.fillOval(ball1x, PANEL_HEIGHT - (int)height1, 10, 10);
         double height2 = initialBall2y - displacement(v02, 9.81, t);
         g.fillOval(ball2x, PANEL_HEIGHT - (int)height2, 10, 10);
         panel.sleep(50); // pause for 50 ms
         panel.clear();
      }
   }
      
   public static double displacement(double v0, double a, double t) {
      return v0 * t + 0.5 * a * Math.pow(t, 2);
   }
}