Curtain - Rod on Accelerating Rail · Physics Brawl 2012 #FoL.1
Physics · mechanics
Problem
Imagine a thin rigid homogeneous rod with mass m = 1 kg and length l = 2 m, which is attached to a horizontal rail by a small massless ring at its end, so that it can slide without friction. As the ring accelerates at a constant rate a = 5 m·s⁻², the rod makes a constant angle φ to the vertical. Find this angle given that the whole situation takes place on the Earth's surface, thus in the presence of the vertical acceleration due to gravity g = 10 m·s⁻², neglecting the effects of air resistance. State your answer in radians.
[Figure: Diagram showing a rod attached to a horizontal rail with acceleration a and gravity g indicated]