Physics Classroom
The Physics Classroom: Introduction to Free Fall
A lesson on free fall covers the fact that free-falling objects do not encounter air resistance and all free-falling objects (on Earth) accelerate downwards at a rate of approximately 10 m/s/s (to be exact, 9.8 m/s/s).
Physics Classroom
The Physics Classroom: 1 D Kinematics: The Big Misconception
An introduction to the ideas behind the misconception and misunderstanding of why all objects accelerate at the same rate. This explanation involves the concepts of force and mass.