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An elevator's protection against overspeed

In the high-rise system described by Otis, a separate governor monitors speed and can trigger safety equipment on the car. Detecting excessive speed and physically stopping the car are different jobs.

3–7 min

Questions you could explore

  • How does the governor know how fast the car is moving?
  • Why are several layers of protection useful?

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Engineering and inventions

How GPS finds you, and fixes its clock

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5–7 min

How GPS finds you, and fixes its clock

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Engineering and inventions

Across an ocean inside a fiber-optic cable

A message crossing an ocean can travel through glass fibers lying on the seabed. The light inside, the layers around it, and the equipment along the route each solve a different problem.

8–10 min

Across an ocean inside a fiber-optic cable

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Engineering and inventions

Bicycle gears and the distance of one pedal turn

Pedaling a bicycle once around in a low gear moves you a short distance with an easy push; pedaling once in a high gear sends you much farther down the road. The ratio of teeth on the front chainring to the rear sprocket explains how a simple chain drive trades pedaling force against distance traveled.

3–5 min

Bicycle gears and the distance of one pedal turn

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An elevator's protection against overspeed | Speech Topic | speaking.app