/* Open Source Physics software is free software as described near the bottom of this code file.
*
* For additional information and documentation on Open Source Physics please see:
*
*/
package org.opensourcephysics.sip.ch02;
import org.opensourcephysics.display.Circle;
/**
* BouncingBall models a falling ball as it bounces off of a floor or a wall.
*
* @author Wolfgang Christian, Jan Tobochnik, Harvey Gould
* @version 1.0 05/07/05
*/
public class BouncingBall extends Circle { // Circle is a class that can draw itself
final static double g = 9.8; // constant
final static double WALL = 10;
private double x, y, vx, vy; // initial position and velocity
double energy;
/**
* Constructs a BouncingBall with the given initial conditions.
*
* @param x double
* @param vx double
* @param y double
* @param vy double
*/
public BouncingBall(double x, double vx, double y, double vy) { // constructor
this.x = x; // sets instance value equal to passed value
this.vx = vx; // sets instance value equal to passed value
this.y = y;
this.vy = vy;
setXY(x, y); // sets the position using setXY in Circle superclass
}
/**
* Steps (advances) the time.
* @param dt double
*/
public void step(double dt) {
x = x+vx*dt; // Euler algorithm for numerical solution
y = y+vy*dt;
vy = vy-g*dt;
if(x>WALL) {
vx = -Math.abs(vx); // bounce off right wall
} else if(x<-WALL) {
vx = Math.abs(vx); // bounce off left wall
}
if(y<0) {
vy = Math.abs(vy);// bounce off floor
}
setXY(x, y);
}
public void calc(){
energy = ((vx*vx)+(vy*vy)/2);
}
}
/*
* Open Source Physics software is free software; you can redistribute
* it and/or modify it under the terms of the GNU General Public License (GPL) as
* published by the Free Software Foundation; either version 2 of the License,
* or(at your option) any later version.
* Code that uses any portion of the code in the org.opensourcephysics package
* or any subpackage (subdirectory) of this package must must also be be released
* under the GNU GPL license.
*
* This software is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston MA 02111-1307 USA
* or view the license online at http://www.gnu.org/copyleft/gpl.html
*
* Copyright (c) 2007 The Open Source Physics project
* http://www.opensourcephysics.org
*/