## Physics Technology Update (4th Edition)

The acceleration of the ball is the gravitational acceleration, whose magnitude and direction are always the same when the object is close to the Earth's surface ($g\approx9.81~m/s^{2}$ downward). It does not matter if the ball is on the way up, on the way down or at the top of its flight. This motion is named free fall. An object is in free fall if it is subjected only to the influence of gravity.