A solid disk of radius R is mounted on an axle that makes an angle θ with the vertical. Initially, the disk is not spinning, and its top surface is covered with dust. Then the disk begins to spin with a slowly increasing angular speed. At what value of the angular speed ω would 75% of the disk surface become dust-free? The coefficient of static friction between the dust particles and the disk surface is µ. The acceleration due to gravity is g.
Many thanks to all contributors and we hope to hear from many more of you in the future!
Note: as always, we would very much appreciate reader-contributed original Challenges.
AAPT members receive access to The Physics Teacher and the American Journal of Physics as a member benefit. To learn more about this member benefit and becoming an AAPT member, visit the Joining AAPT page.