Give learners feedback on their performance to prepare them for formal assessment. Criteria


Yes


The learner(s) can: see the relationship between this exercise and the cable stayed bridge structure. identify the direction of the forces through the cables to the tower. name different parts of the structure.


Activity 5 Model a cantilever bridge Learner’s Book page 28 Guidelines to implement this activity


• This is a whole class activity but with just three people demonstrating it. • We suggest that you choose reliable learners to demonstrate this principle. • Follow the picture in order to position the people taking part. • The centre span in the middle will then support a lighter learner. • When you have demonstrated it once, give others an opportunity to try it for themselves.


Background knowledge


• Use the demonstration given in the Learner’s Book to introduce this concept. A ruler can be balanced on a finger providing there is another finger acting as a counterweight on the shorter side.


• If you live in a rural area, your learners may not have seen a diving board at a swimming pool. However, they may have seen it on the television for big events such as the Olympic Games. The board itself is acting as a cantilever supporting the weight of the diver who is preparing to dive.


• The main boom of the tower crane works on this same principle. There is a large counterweight on the shorter side of the boom with the longer arm stretching out over the construction site.


• Cantilever bridges are heavy steel structures. The Forth Rail Bridge in Scotland is a prime example of this kind of bridge. It takes four years to paint all the steel girders in this bridge. By the time they finish it is time to start again.


Partly


No


51


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