particle2
# circ.p2
# small particle in nearly circular orbit around a more massive one
G 1 # gravitational constant
m 1000
p .5 .5 0 0 # initial pos. & vel. of particle 0
m 10
p .7 .5 0 31.6228 # initial pos. & vel. of particle 1
# if potential is proportional to log(r),
# m is mass of central particle,
# central particle is still,
# ratio of masses is very high,
# and tangential speed of outer particle is sqrt(Gm)
# then a circular orbit results.
# in this example, sqrt(Gm) = sqrt(1*1000) = 31.6228