"why burn your bridges when you can blow your bridges up"

so, in our consturction/structures class we were given the task to create a bridge that was 2 feet long, 6 inches wide and capable of holding extreme loads. But the catch was that it could only weigh 4 ounces(which is similar to 4 fluid ounces if you want to picture the weight of the last 1/3 of beer minus the can weight). There was a scale and you were disqualified if you went over. so, my friend jeff and i used balsa wood (the kind you use for small toy airplanes)on its strong side for our bridge. The class had a competition of bridge destroying, which was a helluva good time. Based on our material we decided to go with a classic arch/mountain-pass bridge with diagonal trusses and our little feather-weight bridge a monster holding over 70 lbs.