/* 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 */