
96 Chapter 2 Force and Motion
For this reason, the space shuttle travels around the earth along a circular (or, more
specifically, elliptical) path. The feeling of so-called zero-gravity is created because the space
shuttle and everything inside it, including the astronauts, are “falling” at the same gravita-
tional acceleration.
Understanding Parabolic Motion
We examined a ball in flight on page 75—that ball’s motion is something we call parabolic
motion. Here, let’s take a more in-depth look at the ball’s flight using some real numbers
and equations.
In the figure below, the distance in the horizontal direction is expressed as x, the verti-