--- title: Building strong things: bridges, towers and shapes — a lesson of Mova's school · trees and pragmatics description: «Building strong things: bridges, towers and shapes», a lesson of the world course of Mova's primary school, sentence by sentence with dependency trees and pragmatics. It begins: Builders think about two kinds of force inside a structure. --- [Mova](https://md.mova.elamur.ai/free/en/) · [this page in HTML](https://mova.elamur.ai/free/en/corpora/school/world/86-building-strong-things/) [home](https://md.mova.elamur.ai/free/en/) / [corpora](https://md.mova.elamur.ai/free/en/corpora/) / [school](https://md.mova.elamur.ai/free/en/corpora/school/) / [World](https://md.mova.elamur.ai/free/en/corpora/school/world/) / Building strong things: bridges, tower… # Building strong things: bridges, towers and shapes Lesson 86 of the world course of Mova's primary school: 27 sentences, each with its syntax tree and pragmatics. The lessons are written for Mova, and their agreed trees are part of Mova corpus 0.4 (CC BY-SA 4.0). How Mova does on its tests: [the lesson at school](https://md.mova.elamur.ai/free/en/school-run/world/86-building-strong-things/). - [0](https://md.mova.elamur.ai/free/en/corpora/school/world/86-building-strong-things/0/) — Builders think about two kinds of force inside a structure. - [1](https://md.mova.elamur.ai/free/en/corpora/school/world/86-building-strong-things/1/) — Compression squashes a part, like the legs of a table under a heavy load. - [2](https://md.mova.elamur.ai/free/en/corpora/school/world/86-building-strong-things/2/) — Tension stretches a part, like a rope holding up a swing. - [3](https://md.mova.elamur.ai/free/en/corpora/school/world/86-building-strong-things/3/) — Stone and concrete are very strong when squashed but crack easily when stretched; steel is strong in both ways. - [4](https://md.mova.elamur.ai/free/en/corpora/school/world/86-building-strong-things/4/) — The triangle is the strongest simple shape for a frame. - [5](https://md.mova.elamur.ai/free/en/corpora/school/world/86-building-strong-things/5/) — Push on the corner of a square frame made of sticks and it folds into a slanted shape, but a triangle cannot change its shape unless a side breaks. - [6](https://md.mova.elamur.ai/free/en/corpora/school/world/86-building-strong-things/6/) — That is why cranes, roofs, pylons and the Eiffel Tower are full of triangles. - [7](https://md.mova.elamur.ai/free/en/corpora/school/world/86-building-strong-things/7/) — Bridges come in different kinds. - [8](https://md.mova.elamur.ai/free/en/corpora/school/world/86-building-strong-things/8/) — A beam bridge is a flat deck resting on supports. - [9](https://md.mova.elamur.ai/free/en/corpora/school/world/86-building-strong-things/9/) — An arch bridge carries the load around its curve and down into the ground on each side, so every stone is squeezed together. - [10](https://md.mova.elamur.ai/free/en/corpora/school/world/86-building-strong-things/10/) — A suspension bridge hangs its road from strong steel cables slung between tall towers. - [12](https://md.mova.elamur.ai/free/en/corpora/school/world/86-building-strong-things/12/) — A flat sheet of paper flops, but folded into a zigzag or rolled into a tube it can hold up a book. - [13](https://md.mova.elamur.ai/free/en/corpora/school/world/86-building-strong-things/13/) — Hollow tubes are strong and light, which is why bicycle frames and the bones of birds are hollow. - [14](https://md.mova.elamur.ai/free/en/corpora/school/world/86-building-strong-things/14/) — Tall things stay up when they are stable: a wide base and most of the weight low down make them hard to tip over. - [15](https://md.mova.elamur.ai/free/en/corpora/school/world/86-building-strong-things/15/) — Builders also dig deep foundations, so a tall tower does not sink into the ground or lean. - [16](https://md.mova.elamur.ai/free/en/corpora/school/world/86-building-strong-things/16/) — Compression is a force that squashes; tension is a force that stretches. - [17](https://md.mova.elamur.ai/free/en/corpora/school/world/86-building-strong-things/17/) — Stone, brick, concrete and glass are strong in compression but weak in tension. - [18](https://md.mova.elamur.ai/free/en/corpora/school/world/86-building-strong-things/18/) — When a plank or beam bends under a load, its top is squashed and its bottom is stretched. - [19](https://md.mova.elamur.ai/free/en/corpora/school/world/86-building-strong-things/19/) — Steel is strong in both compression and tension. - [20](https://md.mova.elamur.ai/free/en/corpora/school/world/86-building-strong-things/20/) — Reinforced concrete has steel bars inside it so it can resist stretching as well as squashing. - [21](https://md.mova.elamur.ai/free/en/corpora/school/world/86-building-strong-things/21/) — A triangle frame keeps its shape when pushed, but a square frame can be pushed out of shape. - [22](https://md.mova.elamur.ai/free/en/corpora/school/world/86-building-strong-things/22/) — Adding a diagonal strut to a square frame divides it into two triangles and makes it rigid. - [23](https://md.mova.elamur.ai/free/en/corpora/school/world/86-building-strong-things/23/) — An arch carries its load down and outwards into the ground at each end. - [24](https://md.mova.elamur.ai/free/en/corpora/school/world/86-building-strong-things/24/) — A suspension bridge hangs its road from steel cables held up by tall towers, so it can cross a wide river with few supports. - [25](https://md.mova.elamur.ai/free/en/corpora/school/world/86-building-strong-things/25/) — Folding or rolling a sheet of paper makes it much stiffer. - [27](https://md.mova.elamur.ai/free/en/corpora/school/world/86-building-strong-things/27/) — An object with a wide base and most of its weight low down is hard to tip over. - [28](https://md.mova.elamur.ai/free/en/corpora/school/world/86-building-strong-things/28/) — Foundations spread a building's weight into the ground. - ← previous: [Pushes, pulls, friction and wheels](https://md.mova.elamur.ai/free/en/corpora/school/world/85-pushes-pulls-friction-wheels/) - next →: [Electricity at home and staying safe](https://md.mova.elamur.ai/free/en/corpora/school/world/87-electricity-at-home-and-safety/) - ↑ back to [World](https://md.mova.elamur.ai/free/en/corpora/school/world/)