An arch spreads weight along its curve, but the shape of that curve matters. When plywood strips of different lengths bend between two pillars set 500 mm apart, a 650 mm strip creates the strongest arch and holds 16.5 kg. Shorter strips and longer strips both break under less weight, showing that an arch needs the right curve to spread force well.

As force travels along an arch's curve, it splits into two parts. Compression squeezes the material along the surface, while tension pulls at the base where the arch meets its supports. A 650 mm strip creates the strongest arch because its height balances these two forces so neither overwhelms the plywood.

Arches distribute force along their curve, spreading a heavy load so no single spot bears all the weight. The arch's height changes how well this spreading works. A 650 mm strip bent into an arch between pillars set 500 mm apart holds 16.5 kg, more than shorter or longer strips. The taller curve gives force a longer path to travel, distributing the load more evenly across the shape.