/*
 * h3a.java - revised 18 Apr 05 - width 501, height 361
 * @author jackord@kw.igs.net
 */

import java.applet.Applet;
import java.awt.*;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;

public class h3a extends Applet 
                   implements ActionListener {
  int kk=0;                                            // Declarations
  double gr, h;
  String bs="Run"; Button b=new Button(bs);

  public void init() {
    setLayout(new FlowLayout(FlowLayout.LEFT));
    setBackground(new Color(211, 211, 211));
    add(b);
    b.addActionListener(this);
  }

  double rect(int n) {
    double s, x, dx;
    s=0; dx=h/n;
    for (int i=1; i<=n; i=i+1) {
      x=(i-.5)*dx; s=s+1/Math.sqrt(2*gr*(h-x));
    }
    return s*dx;
  }

  public void paint(Graphics g) {
    double x, dx, s1, s2, xa, xb, va, vb, vbar;
    int x1, y1, x2, y2;
    g.setFont(new Font("TimesRoman", Font.PLAIN, 16));
    g.setColor(Color.black);
    g.drawRect(88, 12, 400, 300);
    g.drawString("0", 85, 332);
    g.drawString("5", 485, 332);
    g.drawString("x  (m)", 268, 344);
    g.drawString("0", 72, 318);
    g.drawString("0.4", 66, 18);
    g.drawString("1/V(x)", 16, 133); g.drawString("(s/m)", 24, 203);
    g.setFont(new Font("TimesRoman", Font.PLAIN, 14));
    if (kk==1) {
      gr=9.8; h=4.9; xa=h/8; xb=7*h/8; dx=h/200;
      va=Math.sqrt(2*gr*(h-xa)); vb=Math.sqrt(2*gr*(h-xb)); vbar=(va+vb)/2;
      g.setColor(Color.blue);
      x1=88+(int)(80*xa); y1=312-(int)(750/va);
      for (int i=1; i<=200; i=i+1) {
        x2=88+(int)(80*i*dx); y2=312-(int)(750/Math.sqrt(2*gr*(h-i*dx)));
        g.drawLine(x1, y1, x2, y2); x1=x2; y1=y2;
        if (y1<=12) { i=200; }
      }
      g.setColor(Color.black);
      x1=88+(int)(80*xb); y1=312-(int)(750/vb);
      g.drawLine(x1, 312, x1, y1);
      x1=88+(int)(80*xa); y1=312-(int)(750/vbar);
      g.drawLine(x1, 312, x1, y1);
      g.setColor(Color.green);
      y1=312-(int)(750/va); x2=88+(int)(80*xb); y2=312-(int)(750/vb);
      g.drawLine(x1, y1, x2, y2);
      g.setColor(Color.magenta);
      y1=312-(int)(750/vbar); g.drawLine(x1, y1, x2, y1);
      g.setColor(Color.red);
      y1=312-(int)(750/Math.sqrt(2*gr*(h-xa/2-xb/2)));
      g.drawLine(x1, y1, x2, y1);
      g.setColor(Color.black); s1=rect(20); s2=rect(40);
      g.drawString("Rect:   T(20) = "+(float)s1+"   T(40) = "+(float)s2+
      "   T = "+(float)(s2+(s2-s1)/3), 100, 32);
      g.drawString("Analytic:   T = Tvbar = "+(float)(Math.sqrt(2*h/gr)), 200, 64);
    }
    kk=0;
  }

  public void actionPerformed(ActionEvent e) {         // Button
    String tst;
    tst=e.getActionCommand();
    if (bs.equals(tst)) { kk=1; }
    repaint();
  }
}