### Troublesome Triangles

Many natural systems appear to be in equilibrium until suddenly a critical point is reached, setting up a mudslide or an avalanche or an earthquake. In this project, students will use a simple simulation game to investigate the properties of such systems.

A simple robot to make, plus robots in everyday life to investigate.

What shape and size of drinks mat is best for flipping and catching?

# Straw Scaffold

### Why do this problem?

Building a model scaffold will require students to work in groups.  To be successful, a group will need:
• team work
• good communication
• self-discipline
They will also need to plan their scaffold, testing it as they go to see if their design is fit for purpose.

These are all skills required in Design Technology.

This activity is based on a resource from Richard Hall and Michael Acheson, two of the teachers involved in the very successful STEM teacher inspiration days, 2011-12.  You may also be interested in the resources used in the Dragster workshop on TI day 2.

The practical activity will help students to develop an understanding of forces which will help them in both Maths and Science later on.  Groups should also assess which structure can bear the greatest volume of water for the least number of straws.  To do this, they will need to discuss how they are going to calculate the volume : number of straws ratio to ensure that there is a common criterion in the class.

### Possible approach

This would be an ideal lesson for a visit from one of the Design Technology department, who could lead an initial discussion about how to design and test the scaffold.
For an hour lesson, a suitable division of time would be 40 minutes to test, plan and build the scaffold, and 20 minutes for assessment and discussion.

One way to avoid too much mess is to give groups a beaker and small cubes to test their structure, and only make water available at the final testing.

### Key questions

• How can you compare scaffolds so you can work out which fulfils the brief best?
• What features characterised successful scaffolds?
• What features characterised successful groups?

### Possible extension

• Finding the maximum amount of water that can be supported by a given scaffold.
• Deciding on whether there are redundant straws in the structures.

### Possible support

All groups should be able to get started at least.  Suggest to a group which is struggling that they start with a smaller scaffold then gradually add height, testing for stability and for load-bearing at each stage.