Theory of the chimney breaking while falling

When a tall isolated chimney or smokestack is destroyed, usually a charge is detonated at its base and the chimney falls in the way a tree falls in that the base remains fixed. The typical photograph of the chimney falling shows it breaking as it falls at a point about one-third its length from the bottom. Application of Newton’s laws of motion to the problem of a long thin chimney of constant mass per unit length shows that there is a maximum bending torque exerted by the upper part of the chimney on the lower when the lower part consists of the lower one-third of the chimney.