1. Feb 25, 2010

### black_hole

1. The problem statement, all variables and given/known data

A 171 kg roller coaster car is on a track that forms a circular loop of radius 45.9 m in the vertical plane. If the car is to just maintain contact with track at the top of the loop, what is the minimum value for its net inward acceleration at this point?

On the Round Up at the amusement park, people stand in a cylindical "room" of radius 5.70 m and the room rotates until it reaches a rotational frequency of 0.17 revolutions per second. At this point, the floor drops out. What is the minimum coefficient of static friction needed so that people will not slide down the wall?

2. Relevant equations

3. The attempt at a solution

1) m = 171 kg, r= 45.9 m
Fnet = Fg
mV^2/r = mag
V^2/r = ag
what do I do from there?

2) r = 5.7 m, V = 35.014 m/s
I know that coeffsliding = Ff/Fn
but what is Fn, what is Fnet

I am confused. help would be greatly appreciated.

2. Feb 25, 2010

### tiny-tim

Hi black_hole!

(try using the X2 and X2 tags just above the Reply box )
What is "a" ?
To find Fnet, use centripetal acceleration and Fnet = ma.