Circular Motion- Just a few quick questions

[alex7298]

Homework Statement

The first problem is "at an amusement park there is a ride in which cylinrically shaped chamber spin around a central axis. People si in seats facing the axis, their backs against the outer wall. At one instant the outer wall moves at a speed of 3.2m/s and an 83kg person feels a 560N force pressing against his back. What is the radius of the chamber?




Second question- "A car is safely negotiating an unbanked circular turn at a speed of 21m/s. The maximum static frictional force actson the tires. Suddenly there is a wet patch in the road reduces the maximum static frictional force by a factor of three. If the car is to continue safely around the curve, to what speed must the driver slow the car?

Homework Equations

For the first problem, i used Fc=mv^2/r
so r=mv^2/Fc...r=(38kg)(3.2m/s^2)/560N=.69, but the answer should be between 1-2. Where am i going wrong?

The Attempt at a Solution

I have no idea where to start for the second question

 

[alex7298]

nvm about the first question. i just realized i put 38kg instead of 83.

now i only need help on the second

 

[alex7298]

the only equations that i can think of that are of any relevance are
Uk=Fk/Fn
Fc=mv^2/r
and that's about it...but i don't know where to start because the only thing it gives you is velocity

 

[rl.bhat]

To negotiate the unbanked curve Fk must be equal to Fc. In both the cases Fn remains constant. Wright down two equations for dry road and wet patch and solve for v.