Maths and Science Day 2012 – Spaghetti Bridges!

The 21st of July 2012 played host to the annual Maths and Science Day. Maths and Science Day allows all year 8 students to work off timetable for the enire day, working in teams to solve scientific and engineering challenges. Deviating from the task of previous years (parachutes for eggs) the teams this year were set the challenge of building a bridge that covers a 50cm span using only spaghetti and hot-melt glue.

The girls got straight to work, ably assisted by Yr 12 students. They worked really well together, with each student contributing to the team design.

Eventually, when all the bridges were built it was time to test them. Bridges were gradually loaded with more and more force until they broke. The winning team would be the one with the highest load:weight ratio. After a nailbiting testing session, a winner was declared – Team 25 with a load:weight ratio of 11:1!

Bridge 25 – the winning bridge!

After this the teams got together to create a poster explaining their design, the science behind the engineering of bridges and an evaluation of their bridges performance. Team 10 were judged to have the best poster for their careful analysis of why their bridge collapsed with only 10g on it!

A spaghetti bridge, inspired by a Warren Truss bridge

Every team worked incredibly well – their bridges may not have held a great load but they all produced a structure which they could be proud of.

Testing bridges

Funding for the purchase of the hot-melt glue guns and the spaghetti was kindly provided by the Institute of Physics (IoP) http://www.iop.org/ , so many thanks to them for making this event possible.

Non Newtonian fluids

Many people have heard of Sir Isaac Newton. He is famous for developing many scientific theories in mathematics and physics. Newton described how ‘normal’ liquids or fluids behave, and he observed that they have a constant viscosity (flow). This means that their flow behaviour or viscosity only changes with changes in temperature or pressure. For example, water freezes and turns into a solid at 0˚C and turns into a gas at 100˚C. Within this temperature range, water behaves like a ‘normal’ liquid with constant viscosity.

Typically, liquids take on the shape of the container they are poured into. We call these ‘normal liquids’ Newtonian fluids. But some fluids don’t follow this rule. We call these ‘strange liquids’ non-Newtonian fluids.

The viscosity ( how “runny” a fluid is) of a non-Newtonian fluid depends on things such as the stress, or pressure applied to them. This means that a quick change in the pressure applied to such a fluid might change its viscosity.

This is the reason that explains the formation of these cornflour “creatures” . Corn starch is a shear thickening non-Newtonian fluid meaning that it becomes more viscous when it is disturbed. The changes in pressure created by the sound vibrations change the viscosity of the fluid, and the result is fantastic. Check it out here.

Another classic example is Mr. Tickle walking on custard.