Classical Dynamics of Particles and Systems · Problem 11-8
Coupled Oscillations — Marion & Thornton
Physics — Mechanics · door-closing-hinge-angle
Problem
A door is constructed of a thin homogeneous slab of material: it has a width of 1 m. If the door is opened through 90°, it is found that on release it closes itself in 2 s. Assume that the hinges are frictionless, and show that the line of hinges must make an angle of approximately 3° with the vertical.