We’re going to be talking about structures today and why things stand up.
If we make a triangle shape, it will be stiff even if the joints let the sides rotate. If we make a square shape, the joints have to be stiff for the square to keep its shape. If you push a corner of the triangle in any direction, you push and pull the sides, and they hold the corner still. In a square, they don’t unless the corners are stiff. It’s easier to make stiff sides, than stiff corners.
Using paper building blocks (https://babbledabbledo.com/science-for-kids-paper-building-blocks/), build a tower.
Break for Drink and Snack – in aid of Save the Children’s Den Day, we will be building a big den to eat our snack in and all donations will be going to Save the Children.
Buildings are made of lots of different materials, we’re going to do an experiment to look at some differences between different materials and how they react to stress.
I’ve got three rods which are all the same diameter (4mm knitting needles made of bamboo, plastic and stainless steel). I am going to attach weights to them and mark on this paper how far they bend.
Set up the first rod, attach it firmly in place, measure 20cm along the rod and tie a string to hang the weight. Which rod bent the most? Which one bent the least? Which material would make the best hook?
Add greater weights and see how much weight must be added to take the material past its ‘plastic point’ where it will not spring back after the weight is removed.