Roller coasters: would we fall out without restraints?

[helpmeplz!]

I ask because as you might have heard recently a person fell out of a roller coaster when her restraint came open last week in Ohio. I was always told that the physics of these ride designs made it so that the people would be safe even without a restraint.

I'm skeptical about a few things first of all.

Consider a roller coast going around a loop. On the bottom of the loop you obviously don't need the restraints because gravity is pushing you onto your seat. But at the top of the loop, your seat is above you with respect to the ground, and so there is no support against your weight. But of course you have a component of velocity upwards and your velocity decreases but your change in height is perfectly in line with the coaster and the track, and so you don't fall. Is this the jest of it?

But wouldn't this be disregarding an important thing. What if when your restraint opens, you were to roll? In other words if you weren't able to stand completely still, that would end pretty badly for you wouldn't it?

Also if your restraint opened and you were going around a curve and again you were to roll.

Another question, you know those rides that boost you up all of a sudden and then stop at a certain level? What would happen if your restraint opened as you were going up, and as the ride slows down your velocity is bigger and so you end up too high at the top and fall off?

Am I right in my concerns or am I missing something?

 

[russ_watters]

Not all of the g-forces are vertical, much less downward with respect to the train. I was recently at Hershey Park and one coaster, Skyrush, has only a lap restraint, yet pulls -2g, which is pretty disconcerting:
http://en.wikipedia.org/wiki/Skyrush

Barrel rolls in particular can throw you from one side to the other.

 

[chrisbaird]

"I was always told that the physics of these ride designs made it so that the people would be safe even without a restraint." You were told wrong. That used to be true of many of the older, safer, slower rides. As an extra precaution, designers aligned the g-forces to keep a person in their seat even without restraints. In a push for every faster and crazier rides, most rides these days depend crucially on the restraint. Any ride with barrell rolls, jerky motions, or parts where the riders are pushed against the restraint instead of away from the restraint relies on the restraint to keep riders in their seats.