// This program computes the trajectory of a projectile.

import java.awt.*;

public class Projectile {
    // constant for Earth's gravity acceleration in meters/second^2
    public static final double ACCELERATION = -9.81;
    public static void main(String[] args) {
        DrawingPanel panel = new DrawingPanel(420, 220);
        Graphics g = panel.getGraphics();
        table(g, 60, 50, 10);

        g.setColor(Color.RED);
        table(g, 50, 80, 50);
    }

    // prints a table showing the trajectory of an object given
    // its initial velocity v and angle and number of steps
    public static void table(Graphics g, double v0, double angle, int steps) {
        double radians = Math.toRadians(angle);
        double v0x = v0 * Math.cos(radians);
        double v0y = v0 * Math.sin(radians);
        double totalTime = -2.0 * v0y / ACCELERATION;
        double dt = totalTime / steps;

        System.out.println("    step       x       y    time");
        for (int i = 0; i <= steps; i++) {
            double time = i * dt;
            double x = displacement(v0x, time, 0.0);
            double y = displacement(v0y, time, ACCELERATION);
            System.out.printf("%8d%8.2f%8.2f%8.2f\n", i, x, y, time);
            g.fillOval((int) x, (int) (220 - y), 5, 5);
        }
    }

    // returns the horizontal displacement for a body
    public static double displacement(double v, double t, double a) {
        return v * t + 0.5 * a * t * t;
    }
}