For a tandem skydiver, the fastest part of your skydiving experience is the freefall. As you may have guessed, freefall is the time between when you exit the airplane and when you deploy your parachute. During this time, you are falling free, but not necessarily freefalling! The reason is semantics: technically, the physics definition of freefall is the downward movement of an object under the force of gravity alone.
As a tandem pair falls, the force of gravity acts upon them but so does something else. Though, it may seem like the air is “empty,” it is composed of many invisible air molecules. As the tandem skydiving pair falls, they collide with these particles, and the air particles are pushed aside much like a swimmer pushing his or her way through the water. The collision with these air particles creates air resistance (or drag) and prevents the falling object from infinitely increasing speed. So, your ultimate speed has to do with something called terminal velocity.