## CSE 142 Python, Autumn 2008
## This program displays the motion of a thrown projectile over time.
##
## Written in Java by Marty Stepp
## Ported to Python by Ian Gienger

from math import *
from drawingpanel import *

GRAVITY = -9.81

# Plots the motion of a single projectile with the given
# initial velocity v0, angle, and number of steps to plot.
def projectile(panel, v0, angle, steps, color="black"):
    # v0y = v0 sin theta, v0x = v0 cos theta
    v0y = v0 * sin(radians(angle))
    v0x = v0 * cos(radians(angle))

    # t = -2v0 / a
    totalTime = -2 * v0y / GRAVITY
    dt = totalTime / steps

    print "       x       y      time"
    for i in range(steps + 1):
        t = i * dt
        x = v0x * t
        y = displacement(v0y, GRAVITY, t)
        print "%8.2f %8.2f %8.2f \n" % (x, y, t)
        panel.canvas.create_oval(x, 300 - y, x + 5, 305 - y,
                                 fill=color, outline=color)
        panel.sleep(dt * 100)

# Computes and returns the change in position of a projectile
# given its initial velocity v0, acceleration a, and time t.
def displacement(v0, a, t):
    return v0 * t + 0.5 * a * t**2

# Main
panel = DrawingPanel(400, 300)

projectile(panel, 30, 85, 20)
projectile(panel, 60, 85, 50, color="red")
projectile(panel, 120, 85, 100, color="green")