## Oct. 1, 2002, A. Middleton
## orbittype.py
## This code simulates the motion of an object subject to a force
## from another object that is fixed at the origin (0,0,0).

from visual import *
scene.autoscale = 0

forcetype = -2

## draw object at origin in a suggestive yellow color
sphere(radius=0.2, color=color.yellow)

## this will be the flying object, suggestively named and
## colored
earth = sphere(radius = 0.1, color=color.blue, pos = (1,0,0))
## Give it a nonzero velocity, so that it will not plummet
earth.vel = vector(0,0.8,0)

dt = 0.01

while 1:
    rate(80)
    earth.pos = earth.pos + dt * earth.vel
    earth.vel = earth.vel + dt * (-earth.pos*mag(earth.pos)**forcetype)