ur_mum.gif

import java.util.Scanner;

/**
 * Created by Edwin on 11/11/2014.
 */
public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        double vinput, anglein, angleinradians, c, m, voutput, vx, vy, ff, fg, ffy;
        double ffx, fnety, fnetx, dx, dy, ay, ax, totaldisplacement, height;
        /*
         * Index of variables, in order:
         * [calder, list them here]
         */
        boolean doISeriouslyHaveToKeepLooping = true;

        totaldisplacement = 0;
        height = 0;
        System.out.println("Enter the magnitude of the launch velocity.");
        vinput = in.nextDouble();
        System.out.println("Enter the launch angle.");
        anglein = in.nextDouble();
        angleinradians = anglein * 0.01745329251; //Multiplied by 2pi/360 to convert to radians.
        c = 0.3; //Most simulations use 0.3. Using the cd = 2Fd/(ρ*v^2*A) equation, I got 0.298.
        m = 0.144; //The baseball was massed in class.
        while (doISeriouslyHaveToKeepLooping == true) {
            vx = vinput * Math.cos(angleinradians);
            vy = vinput * Math.sin(angleinradians);
            ff = vinput * Math.pow(c, 2); // Ff = cv^2
            ffx = ff * Math.cos(angleinradians);
            if (vy > 0) {
                ffy = ff * Math.sin(angleinradians); //this is in the DOWN direction.
                //If the object is travelling upwards, the resistance will be in the down direction.
            } else {
                ffy = -ff * Math.sin(angleinradians);
                //If the object is travelling downwards (ay is negative), air resistance will be applying a force upwards.
            }
            fg = 9.8 * m;
            fnety = ffy + fg; //[down]
            fnetx = ffx; //[bckwd]
            ay = -fnety / m; //[up]
            ax = -fnetx / m; //[fwd]
            dx = vx * 0.01 + 0.5 * ax * Math.pow(0.01, 2);
            dy = vy * 0.01 + 0.5 * ay * Math.pow(0.01, 2);

            totaldisplacement = totaldisplacement + dx;
            height = height + dy;
            vx = vx + ax * 0.01;
            vy = vy + ay * 0.01;
            angleinradians = -Math.atan(vy / vx);
            if (totaldisplacement > 40) {
                doISeriouslyHaveToKeepLooping = false;
            } else {
                doISeriouslyHaveToKeepLooping = true;
                System.out.println(height); //We want height to be 0 when the loop ends.
                //This ensures our trajectory will be as desired.
            }
        }
    }
}