Free Fall rides have three parts to them that you experience when you ride them:
1.) the ride up
2.) the momentary suspension
3.) the downward plunge

Ride Up
To bring both the car & passengers to the top of a free-fall tower, a force has to be applied. This force is applied by motors.

Downward Plunge
    The car is suspended at the top of the tower and eventually plunges downward. The car accelerates with only gravity influencing it. All objects fall with the same acceleration regardless of their mass. With the downward plunge.... you experience weightlessness.

Gravity and weightlessness
    Gravity, the only force acting on the car and its contents when it falls, is 9.8 m/s^2. To calculate the velocity of a free falling object you can use the equation: velocity = acceleration* time traveled (v=at). Manipulated versions of this equation are:                     a=v/t and t=v/a. 
    For free fall rides you can put the value of gravity (9.8m/s^2) as acceleration since only gravity is acting on it.
    To understand weightlessness, you have to understand a few things. When you first sit on a seat of a ride, there are two forces acting on you that are equal to each other. These two forces are normal force, the force on the seat pushing you upward, and the force of gravity, pushing you downward.
    On some rides, one may feel a sense of weightlessness. What you actually experience when you feel weightlessness is a small or no normal force when you're dangling above the seat of a ride, because the seat isn't pushing upward on you since you're falling at the rate equal to the pull of gravity. Without the normal force, you can't feel your weight and in turn you won't be able to feel the force of gravity. Only the value of normal force changes, your weight and the value of gravity doesn't ever change.    

Potential & Kinetic Energy
    Potential energy builds up as the car goes up the tower and is at its max. when you reach the top. This potential energy is changed into kinetic energy as the car falls downward. Kinetic energy has reached its max. and all potential energy is used up when the car reaches the bottom of the tower. 
    Some of the potential energy is lost to friction, so kinetic energy will not be equivalent to potential energy. To find the value of kinetic or potential energy, you can use these equations: 
           KE = ½*m*v^2 and PE = mgh.