* Free fall means only gravity acts: By definition, free fall means an object is only under the influence of gravity.
* Gravity causes acceleration: Gravity is a force, and forces cause acceleration. This means any object solely under the influence of gravity will experience acceleration.
Important Note: We often say an object in free fall is "weightless" or experiences "zero gravity." This is a bit of a misnomer. The object is still under the influence of gravity and accelerating, but it's not experiencing a normal force from a surface (like the ground or a chair) to counteract that acceleration. This is what makes it feel weightless.
Example: A skydiver jumping out of a plane is in free fall. They are accelerating towards the earth due to gravity.
