Moments and beams on supports
A moment measures a force's turning effect: force × perpendicular distance from the pivot. A beam in equilibrium has zero resultant force and zero resultant moment about every point. Take moments about a support to remove its unknown reaction.
≈ 35 minTilting and non-uniform rods
A beam on two supports is "on the point of tilting" about one support when the reaction at the other support becomes zero. A non-uniform rod's weight acts at its centre of mass, which isn't the midpoint; treat its distance as an unknown and find it from moments.
≈ 35 min