2 Freely falling bodies The most familiar example of motion with (nearly) constant acceleration is that of a body falling under the influence of the earth’s gravitational attraction. Consider an object moving upward or downward along a vertical axis under the influence of gravity. It has been found that all objects (large or small) experience the same acceleration due to the force of gravity. This acceleration varies slightly with altitude, but for objects near the surface of the earth, the acceleration is approximately constant. It is always directed downward. The value of the acceleration due to gravity g is approximately 9.80m/s2. The value of g is slightly reduced in the high mountains. On the surface of the moon, the acceleration due to gravity is 1.6m/s2. Near the surface of the sun, it is 270m/s2. For a body moving under gravity, and v =v0+gt, y −y0 =v0t+ 1 2 gt2, v2 = v20 +2g(y −y0
