A solid disk is spun clockwise (as viewed from above) to an angular speed while being…
PHYSICS · Single correct · AP · Physics 1: Algebra-based · Force and Translational Dynamics · Force and Translational Dynamics
Problem
A solid disk is spun clockwise (as viewed from above) to an angular speed ω0 while being held above a horizontal surface. The disk is then gently dropped so that its center of mass has negligible horizontal velocity at the moment of contact. Which statement best describes the kinetic friction force exerted by the surface on the disk immediately after contact?
(a) It acts to the left, opposite to the disk’s clockwise rotation, and therefore accelerates the centre of mass to the left.
(b) No kinetic friction force acts because the disk’s centre of mass is momentarily at rest when it touches the surface.
(c) It acts to the right, opposite to the leftward sliding of the rim at the point of contact, thereby accelerating the centre of mass to the right while reducing the disk’s angular speed.
(d) It acts to the right, in the same direction the rim is sliding, and therefore decreases the disk’s linear speed but increases its angular speed.