Building a bride out of cardboard, straws and string

Question

​Hey, 

I have an assignment in my physics class where I have to build a bridge out of:

 a 20cm x 8cm piece of cardboard, 

10 straws, 

And 3 meters of string. 

How it works:

The bridge will be placed on 2 pieces of metal that are 15cm apart from each other. 

There will be a bucket hanging on a small bar in the middle of the bridge with weight in it. 

The bridge able to carry the most weight wins. 

Rules: 

The maximum of straws over the "length" of cardboard (to support the cardboard itself) are 4

No other materials may be used, means I have to connect everything just with the string. 

My Idea: 



Since the triangle is the strongest shape I would place two "pyramids" on the right and the left of the top side of the bridge so when the bridge bends in in the middle, they would help putting the weight to the outside. 

Any ideas on how to build it??? 

Thank you very much! 

Answer 1

I'm thinking you might want to take advantage of the string in conjunction with the triangles. Perhaps a suspension bridge with string also going through the triangle supports. You don't say if you get to glue it or tape it together though so ??

Maybe something like this (where the red string goes through the triangle supports and the blue string is for suspension). You, of course would need additional support across and also to tie the suspension string to the "road" but it could work.