ten little fingers - arvind gupta (4 mb pdf)

1. Everything has a structure. Thehuman body, buildings, bridges all havea skeletal frame which bears the load.Using old postcards we will explore afew structures All postcards are 14-cms. long and 9-cms wide.POSTCARD STRUCTURES2. Roll a postcardinto a cylinderand glue its edgeto make a 9-cm9cmtall cylinder. Itdoes not lookvery strong. Howmany loads can itsupport? Make aguess?3. Slowly place books on the cylinder so that theydo not tip off. Keep piling books until the cylindergets crushed The 9-cm tall postcard cylinder willbe able to support almost 4- kgs of books. Are yousurprised? Make square, triangular and ovalcylinders. Which cylinder can bear more load?4. Now fold postcards in various cross-sectionsto make 14-cm high columns. Which cylindercan bear the most load? Why? Have youwondered why tree trunks are circular and nottriangular or square? For a fixed perimeter thecircle encloses the maximum area.5. Stand two bricks 12-cm apart. Placea postcard on top so that 1-cm. of thecard sits on each brick. Place a 50-paisecoin (5gms) on the card. The postcardsags. When the load is 40-gm thepostcard caves and falls down.6. Fold zigzag, fan shaped pleats in the postcard. Itcan almost support 1-Kg. Are you surprised? It is nomore a material, but has become a structure. Theshape of the material gives it strength. Corrugated tinroof sheets are an example of increased strength.7. Crease postcards to make a right-anglesection, a U channel and a T beam. Dodifferent sections bear different loads?8. Place the 14-cm long column as beams between twobricks. Hang a shoe tin pan and place weights in it. Whichcross-section of beam supports the maximum load?