# Homework Help: Floor Drop Ride

1. Nov 1, 2007

### habs.fan

1. The problem statement, all variables and given/known data
In a ride called Drop Out, riders are spun in horizontal circles of radius 5.5m, which forces them to the outer wall. When they are spinning fast enough, the floor drops out, and they are suspended by friction. The coefficient of static friction is 0.28, how many rev/s must the ride acheive before the floor is allowed to drop out?

2. Relevant equations
a$$_{}c$$ = rv^2

3. The attempt at a solution
I'm sort of lost for what to do, I have an FBD with G (down) and Friction (up), I also know the centripetal acceleration will be along the radius, towards the center of the circle, but I do not know how to solve this one.

2. Nov 1, 2007

### Dick

No, a=v^2/r. If you know the centripetal acceleration, then you know the normal force. You then can relate the frictional force to the normal force, et voila. Please continue.

3. Nov 1, 2007

### habs.fan

ok so...ac = v^2/5.5
v is unknown though, so we don't really know the centripetal acceleration?

4. Nov 1, 2007

### Dick

You know the radius, and v can be expressed in terms of the angular velocity. Leave it unknown. That's what you want to solve for.