PT 1.4 - Testing of Bridge

The video above shows our bridge test. Although it doesn't show the breakage, our bridge tested and held onto 30kg before breaking.

Mass of bridge=124 grams/0.124kg
Mass that bridge held up=30kg
Efficiency of bridge=30kg/0.124kg

This is our bridge after the testing.
Upon close inspection, it turns out that the structural failure was due to 2 of the links. 
This was probably due to the fact that our bridge is really thin, therefore it wobbled during the testing. The wobbling caused stress to be exerted sideways,  instead of vertically as it was designed. 

4.3   Discussion of bridge design after testing

What is your score on efficiency? If the efficiency is high/low, what went right/wrong?   

242, the efficiency was high because there was a strong support and had a good design, however the efficiency could be improved as 2 of the ice cream sticks were not glued well, we believe that we would have done better if not for that. Also the bridge was hastily built and had some imperfections in the build quality resulting in the unbalanced distribution of force. Therefore some parts of the bridge experienced more stress than others although the thickness of the bridge at various parts was relatively the same.

Which part of the bridge started to give way first? Explain using Physics concepts.

The part in the middle, because the distance is greatest from the supports and since Force*distance=moment. Therefore the moment is the greatest at that point and stress will be the highest there.

Which part of the bridge provided the most strength in the testing process? Explain using Physics concepts.  
The truss below as it is made out of many layers of ice cream sticks and it provided support to the main bridge through the links. 

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