puentes

http://www.rtve.es/alacarta/audios/no-es-un-dia-cualquiera/no-dia-cualquiera-puentes/3395449/

http://www.pbs.org/wgbh/buildingbig/bridge/basics.html

https://www.pinterest.es/pin/357473289146094452/

https://evavarga.net/toothpick-bridges-lesson-plan/

http://www.pbs.org/wgbh/buildingbig/lab/loads.html