In a popular amusement park ride, a rotating cylinder of radius 3.5 m is set in rotation at an angular speed of 5.28 rad/s, as shown. The floor then drops away, leaving the riders suspended against the wall in a vertical position. What minimum coefficient of friction between a rider's clothing and the wall of the cylinder is needed to keep the rider from slipping? The acceleration of gravity is 9.8 m/s2 .