Tuesday, 6 December 2011
Today we worked on our last bridge project - a suspension bridge. We had already seen a documentary about the worlds longest suspension bridge and we had a quick look at a picture of a suspension bridge to remind ourselves what they are like. We made ours from Duplo, Cardboard and string but we discussed the types of materials used to build a real bridge.
First we constructed the towers and the suspension cables anchored to the ground.
I showed R how to use an awl to make holes in the card road section.
Dad threaded the strings through and knotted them underneath the roadway.
The roadway was tied onto the main suspension cable and tested with a car.
Now to test the bridge to destruction...
We used all the wooden blocks and weights that we had (2.47kg). The bridge still held!
So we tried adding some heavy boxes from the store cupboard (5.56kg) - it still held...
So we went to the garage and tried some house bricks that were lying around. Finally it broke with 2 house bricks.
As you can see it was only one cable that had become detached from the anchor point that caused the bridge to fail
Conclusion - suspension bridges are REALLY strong!