The Big Idea Kids should find that adding the cables to their straw bridge and anchoring the cables on both sides significantly increases the load that the bridge can support. A suspension bridge's cables and towers transmit the dead load of the bridge deck and the live load of traffic to the massive anchor blocks at each end of the bridge. The tension in the cables leading up from the bridge deck is balanced by the tension in the cables leading to the anchor blocks, as well as the compression in the towers. The anchor blocks must be massive enough to resist the tension in the cables caused by the weight of the bridge deck. Kids can make their bridge decks longer by creasing the end of one straw and inserting it into the end of another straw.
Kids can try to build as long a bridge as possible that can support a given amount of weight.
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