How much weight can an arch hold before it breaks? Arches distribute force along their curve. A flatter arch handles force differently than a tall one. You cut plywood strips of equal width but eight different lengths. Each strip bends into an arch between two pillars set 500 mm apart. A longer strip creates a taller arch. You hang a pail from the center of each arch and add water until the plywood snaps. A scale measures the final weight. The strongest arch uses a 650 mm strip and holds 16.5 kg. Shorter strips break under less weight. Strips longer than 650 mm also hold slightly less.