A 1.0 kg solid cylinder with a radius of 15 cm is rotating at an angular speed of 230 rpm about its central frictionless axis. You want to stop the cylinder in 30 s by applying a friction force f to the outer edge. Determine the magnitude of f.

• A. 0.06 N
• B. 0.1 N
• C. 2.3 N
• D. 5.6 N

Answer: (A)