Teacher Demonstration 22 Incredible Can Strength Materials: • Empty Aluminium Can • Books (eg encyclopedias) • Broomstick • Flat piece of wood (if floor is carpeted) Instructions How many encyclopedias can an ordinary, empty aluminium soft drink can support? 1 Set a can on a smooth flat floor. Discuss some aluminium can trivia (see Teacher Notes). Centre a large, hardcover book on top of the can. The more accurately you centre this book, the less wobbly your growing stack will be. Ask the class to predict how many books the can will hold before it is crushed. Note: put a flat piece of wood on the floor if your classroom is carpeted 2 Start adding books. Centre each one as accurately as possible. Ask volunteers to help stabilise the stack if it becomes too wobbly. Safety note: volunteers should be wearing enclosed shoes in case the stack falls 3. A huge stack of books balancing on a can like this will get students very excited. 4. Don’t be afraid to show your excitement too… this really is amazing! Teacher Demo 22 – Super Can | Page 1 © 2008 Ruben Meerman | ABC Science Online 5. If you run out of books to stack on the can, gently tap its side with a broomstick. The slightest dint will cause the can to collapse under the weight. 6. This can held 52kg before finally collapsing… one tough little bit of aluminium! You could repeat the demonstration with a slightly, and a very dinted can to see demonstrate the impact of minor defects on the can’s strength. Teacher notes The can is able to support such a huge weight because of its cylindrical shape. When loaded carefully, cylinders distribute weight evenly through their walls but the slightest defect can greatly reduce a cylinder’s strength. Aluminium Can Facts An aluminium can weighs just 15 grams which is equivalent to three candy coated chocolate buttons. The walls of an aluminium can are just 0.11mm thick – about the diameter of an average human hair. Australians use more than three billion aluminium cans per year. The energy required to produce one aluminium can is the same as the amount of energy used to recycle 20 aluminium cans. That’s because aluminium has to be extracted from the bauxite which requires huge amounts of energy. One tonne of recycled cans saves five tonnes of bauxite. Teacher Demo 22 – Super Can | Page 2 © 2008 Ruben Meerman | ABC Science Online .