Does high speed or high acceleration provide the biggest thrill on an amusement park ride?.
It is not necessarily high speed or high acceleration that creates a thrill for the amusement park patron but instead it is the forces applied to the body during a ride - forces created by high speed and acceleration. On amusement park rides there are two main forces acting on your body that you noticeably feel and enjoy. These forces are g force and centripetal force.
When a body is at a constant velocity all forces are in equilibrium. Imagine a car on the highway travelling at a constant velocity. We can say that after taking account of internal friction and the rolling resistance of the tyres we have an amount of thrust (force) that is equal to the amount of aerodynamic drag (force). Imagine now, that this car accelerates. At present your body should be experiencing 1G. This means that in our present gravitational environment all objects, if not already experiencing a normal force say, of the ground, will accelerate at 9.8m/s. If the car accelerates in a forward direction at 9.8m/s you will feel a force equal to that of gravity, 1G, pushing you back into your seat. The difference here is that this force is working on your body horizontally as well as vertically. If you double the rate of acceleration to 19.6m/s,.
your body would experience a G force double what is usually experienced. This means that your weight has doubled - your mass has stayed the same but your weight has doubled. It will take double the amount of energy to move your body against this G force. If, in a roller coaster you were accelerated forward in a horizontal direction at a rate of 9.8m/s, you would feel the force of 1G applied to your body horizontally. This is not natural to you. This confuses your body. This is what creates the thrill. If you were to be accelerated any more than 9.8m/s, the force acting on your body horizontally would feel even more unnatural and even more thrilling.