文档介绍：Chap1-5 Free Fall and the Acceleration of Gravity
1 Introduction to Free Fall
A free-falling object is an object which is falling under the sole
influence of gravity. That is to say that any object which is moving and
being acted upon only be the force of gravity is said to be "in a state
of free fall." This definition of free fall leads to two important
characteristics about a free-falling object:
• Free-falling objects do not encounter air resistance.
• All free-falling objects (on Earth) accelerate downwards at a rate of approximately 10
m/s/s (to be exact, m/s/s)
Because free-falling objects are accelerating downwards at at rate of 10
m/s/s (to be more accurate - m/s/s), a ticker tape trace or dot diagram
of its motion would depict an acceleration. The dot diagram at the right
depicts the acceleration of a free-falling object. The position of the
object at regular time intervals - say, every second - is shown. The
fact that the distance which the object travels every interval of time
is increasing is a sure sign that the ball is speeding up as it falls
downward. Recall from an earlier lesson, that if an object travels
downward and speeds up, then its acceleration is downward.
This free-fall acceleration was witnessed in class in a demonstration
involving a strobe light and a dripping jug of water. The room was darkened