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Retractile drawbridge

Retractile drawbridge is a engineering topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Retractile drawbridge rather than just read about it. In short: A retractile drawbridge is a rare type of moveable bridge in which the span is pulled away diagonally on rails. It is a variant of the retractable bridge.

Retractile drawbridge — main illustration
Retractile drawbridge — illustration

Key takeaways

  • Retractile drawbridge belongs to engineering; place it in that map before memorising details.
  • Learn the definition first, then one example that makes the definition concrete.
  • Connect Retractile drawbridge to a quantity you can measure, compute or draw — that is where exam questions come from.
  • Reproduce the core statement of Retractile drawbridge from memory before moving on to harder problems.

Reference excerpt

A retractile drawbridge is a rare type of moveable bridge in which the span is pulled away diagonally on rails. It is a variant of the retractable bridge. Only four examples are known to exist in the United States. It is believed to have been invented by T. Willis Pratt in the 1860s.

See also Carroll Street Bridge, the country's oldest surviving retractile bridge, located in Gowanus, Brooklyn Summer Street Bridge, an example of this type of bridge, located in Boston, Massachusetts, U.S.

References

Illustrations

Retractile drawbridge: Boston's Summer Street Bridge in July 1925, showing the tracks for the retractable sections to slide on
Boston's Summer Street Bridge in July 1925, showing the tracks for the retractable sections to slide on

Worked examples

Example 1 — a first encounter with Retractile drawbridge

Start with the simplest possible case. Write down what Retractile drawbridge claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In engineering, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Retractile drawbridge before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Retractile drawbridge ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Retractile drawbridge

In research
Retractile drawbridge appears in engineering research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry
Engineering practice reuses Retractile drawbridge in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom
Retractile drawbridge is common in secondary-school and first-year university syllabi. It links to neighbouring topics Bridge (structure) stubs, Bridges, Building and structure type stubs, so understanding it makes those chapters shorter.
In everyday life
Look for Retractile drawbridge outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.
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How to study Retractile drawbridge in 20 minutes

  1. Read the reference excerpt below once, without taking notes.
  2. Close the page and write down what Retractile drawbridge means in your own words.
  3. Compare your version with the excerpt and mark what you missed.
  4. Work through the three examples above with pen and paper.
  5. Explain Retractile drawbridge out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Retractile drawbridge in simple terms?

A retractile drawbridge is a rare type of moveable bridge in which the span is pulled away diagonally on rails. It is a variant of the retractable bridge.

Why does Retractile drawbridge matter?

Because it connects several engineering ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Retractile drawbridge?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Retractile drawbridge.

Tags

  • Bridge (structure) stubs
  • Bridges
  • Building and structure type stubs

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