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Ece's Bridge: Squares Slanted, Triangles Stood
Ece's craft-stick bridge made of squares collapses before the first liter of water is even full. By testing a square and a triangle tied with string, plus a triangle with a rubber band, she discovers why a triangle holds its shape—and builds a triangular bridge that supports seventy-five times its own weight.
Page 1
A craft-stick bridge competition was being organized at Ece's school, and the rules had been handed out to everyone. Each bridge had to span the twenty-five-centimeter gap between two desks and be made from no more than twenty wide craft sticks. A bucket would hang right from the middle of the bridge, and water would be poured into it liter by liter using a one-liter measuring cup. Each liter of water weighed one kilogram. Ece was determined to build the bridge that could hold the most water in class, and she set to work planning right away.
Page 2
That evening, Ece laid out the sticks on the kitchen table. Each stick was fifteen centimeters long; joining two of them end to end gave her a bottom edge of thirty centimeters. She placed two more sticks on top and glued three vertical sticks between them to create two squares side by side. That meant one side wall used seven sticks, making fourteen for both walls. Adding three cross sticks at the bottom and three at the top, she used up all twenty sticks.
Page 3
On competition day, Ece placed her bridge between the two desks and hung the bucket from the middle bottom cross stick. Baran slowly began pouring the first liter from the measuring cup. Before even half a liter was filled, the squares leaned sideways and turned into slanted rhombuses. The bridge folded with a snap and crashed to the floor, water splashing from the bucket and wetting the desk legs. Ece stared at the scattered sticks on the floor for a long time, trying to understand what went wrong.
Page 4
That evening, Ece tied four sticks tightly at their corners with string to make a single square. When she pressed lightly on one corner, the square immediately leaned sideways into a rhombus. Next, she tied three sticks together the same way to make a triangle and pressed it just as before, but the triangle did not lose its shape at all. Ece thought about why that was. If the lengths of three sides were set, only one unique triangle could ever be formed, whereas four sides could shift into countless different shapes.
Page 5
Ece wondered about one more thing: What happens when a load is placed on the sides of a triangle? She joined two sticks at the top and stretched a rubber band between the two bottom ends instead of a bottom stick. When she pressed down on the top, the lower ends pushed outward, and the rubber band stretched. That meant the load was pulling on the triangle's bottom edge while squeezing its slanted sides together. If a rigid stick were in place of the rubber band, the bottom edge could not stretch, and the triangle would keep its shape.
Page 6
Ece worked out her new plan by arranging loose sticks across the table. Each side wall would still have two sticks along the bottom, but only one stick centered at the top. Fitting four diagonal sticks between them formed three triangles side by side: two pointing up and one pointing down. One wall used seven sticks, making fourteen sticks for two walls. With three cross sticks at the bottom and two at the top, she would use nineteen sticks in total, keeping one stick as a spare.
Page 7
Ece carefully glued each triangle so their corners joined tightly, then let the glue dry overnight. In the morning, she weighed the bridge on a two-pan balance she had borrowed from school and found it was exactly eighty grams; it was lighter than two eggs. The bottom edge was still thirty centimeters, meaning the bridge would rest two and a half centimeters onto each desk. This time, she decided to hang the bucket from the bottom center joint, right where the corners of the triangles met.
Page 8
On the day of the second attempt, as the whole class gathered around, Baran poured the first liter, then the second, and then the third. Ece bent down and examined the bridge carefully from the side at eye level. The top stick bent ever so slightly, while the bottom sticks stayed straight as a tight wire. Just like in the rubber band experiment, the top edge of the bridge was being compressed, and the bottom edge was being pulled in tension. The triangles passed the bucket's weight from corner to corner, transferring it directly to the desks on either side.
Page 9
Fourth liter, fifth liter, sixth liter... the bucket filled right up to the brim, and the bridge was still standing strong. There were six liters of water in the bucket, meaning it weighed exactly six kilograms. Ece did the math out loud: Six thousand grams divided by eighty grams equaled seventy-five. Her eighty-gram bridge had carried exactly seventy-five times its own weight without collapsing. As her classmates burst into cheers, Baran caught the edge of the gently swaying bucket to steady it.
Page 10
During recess, Baran straightened out a warped square leftover from the first bridge and handed it to Ece curiously. Ece snapped a stick to shorten it and glued it across one corner of the square, running from the middle of one side to the middle of the neighboring side. Once the glue dried completely, Baran pressed on the square with all his might, but it didn't budge—because the little triangle in the corner had locked that angle in place. In the end, Ece neatly lined up her bridge, the corner-braced square, and the rubber-band triangle side by side on the shelf by the window.
