PHYSICS · Single correct · AP · Physics 1: Algebra-based · Torque and Rotational Dynamics · Torque and Rotational Dynamics
Problem
Three identical point masses, each of mass m, are fixed at the vertices of an equilateral triangle of side length a. Consider three axes, all perpendicular to the plane of the triangle:
• Axis 1: through the centroid of the triangle
• Axis 2: through the midpoint of one side
• Axis 3: through one of the vertices
Which axis gives the smallest rotational inertia, and what is the ratio I3/I1 (rotational inertia about Axis 3 divided by that about Axis 1)?
(a) Axis 1; I3/I1=1.5
(b) Axis 3; I3/I1=2.0
(c) Axis 1; I3/I1=2.0
(d) Axis 2; I3/I1=2.0