A couple more odds and ends

After reading Who Sank the Boat, the girls wanted to find out whether a tiny extra weight could really sink an overloaded boat. They set up an experiment with a plastic boat to find out...

#1 took it a little further by experimenting with density. He layered honey, water and oil in a glass and then discovered that some objects will sink through just one or two of the three layers.

Here he is with one of the bridge designs me built at the CSIRO Engineering workshop.