/* From: "COMPUTATIONAL PHYSICS, 2nd Ed" 
   by RH Landau, MJ Paez, and CC Bordeianu 
   Copyright Wiley-VCH, 2007.
   Electronic Materials copyright: R Landau, Oregon State Univ, 2007;
   MJ Paez, Univ Antioquia, 2007; and CC Bordeianu, Univ Bucharest, 2007.
   Support by National Science Foundation                              
*/
// ProjectileAir.java: Calculate projectile motion 
 
import ptolemy.plot.*;
 
public class ProjectileAir  {
     // Static class variables, accessible to all methods (constants)
 static final double v0 = 22., angle = 34., g = 9.8, kf=0.8;
 static final int N = 25;

  public static void main(String[] args) {
		
    double v0x,v0y, T, H, R;
                                                 // Initial constants
    v0x = v0 * Math.cos(angle*Math.PI/180.);
    v0y = v0 * Math.sin(angle*Math.PI/180.);
    T = 2 * v0y / g;
    H = v0y * v0y / (2 * g);
    R = 2 * v0x * v0y / g;
    System.out.println("Frictionless T,H,R = " +T+ ", " +H+ ", " +R);
        
                                  // Create Plot object (from ptplot)
    Plot myPlot = new Plot();
    myPlot.setTitle("Projectile without/with Air Resistance");
    myPlot.setXLabel("x");
    myPlot.setYLabel("y)");
    myPlot.setXRange(-R/20, R);
    
		plotAnalytic (myPlot, 0);          // Plot, no friction, analytic
	  plotNumeric  (myPlot, 2, kf);          // Plot, friction, numeric
                               // PlotApplication display Plot object
    PlotApplication app = new PlotApplication(myPlot);
  }                                                       // end main

  public static void plotNumeric (Plot myPlot, int set, double k)  {
	                                         // Plot, friction, numeric
    double x, y, vx, vy, dt;
    vx = v0 * Math.cos(angle*Math.PI/180.);
    vy = v0 * Math.sin(angle*Math.PI/180.);
    x = 0;
    y = 0;
	  dt = 2 * vy / g /N;
    for (int i = 0; i<N; i=i+1)  {
      vx = vx -k * vx * dt;
      vy = vy - g * dt - k * vy * dt;
      x = x + vx * dt;
      y = y + vy * dt;
      myPlot.addPoint(set, x, y, true);
      System.out.println("x = " + x   + " y = " + y); 
    }
	  myPlot.addPoint(set, x, y, true);
  }                                                // End plotNumeric
 
  public static void plotAnalytic (Plot myPlot, int set)  {  
	                                    // Plot, frictionless, analytic
	  double x, y, v0x, v0y, dt, t;
    v0x = v0 * Math.cos(angle*Math.PI/180.);
    v0y = v0 * Math.sin(angle*Math.PI/180.);
	  dt = 2 * v0y / g /N;
    for (int i = 0; i<N; i=i+1)  {
      t = i * dt;
      x = v0x * t;
      y = v0y * t - g * t * t / 2.;
      myPlot.addPoint(set, x, y, true);
      System.out.println("Frictionless x = " + x   + " y = " + y); 
    }
  }                                               // End plotAnalytic
}                                                        // End class