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Newton had observed that any projectile launched horizontally is, in a sense,
an Earth satellite.
A rock thrown from a tall building sails in a modest
orbit that soon intersects the earth not far from its point of launch.
If the ball
were fired more swiftly to start with, it would travel further. Futher
increasing the speed would result in ever larger, rounder elliptical paths and
more distant impact point. Finally, at one particular launch speed, the ball
would glide out just above the planet's surface all the way around to the other
side without ever striking the ground.
At successively greater launch
speeds, the ball would resolve in ever-increasing elliptical orbit until it
moved so fast initally that it sailed off in an open parabolic or (if even
faster) into a still flatter, hyperbolic orbit, never to come back to its
starting point.
This java applet let you change the launch speed by mouse
click.