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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

Questions you could explore

  • How does the tooth ratio change wheel rotations?
  • What trade-off does a lower gear offer on a hill?

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Engineering and inventions

How GPS finds you, and fixes its clock

Your phone can work out where it is by listening to signals from far above Earth. But turning a signal's travel time into a distance also creates a clock problem: the receiver must account for its own timing error.

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

Induction cooking heats the pan itself

An induction coil uses a changing magnetic field to generate heat in compatible cookware. The choice of pan matters because the heat is not simply conducted from a conventional burner. Explore how the energy reaches the cookware, and why the cooktop surface can still become hot from the pan.

3–5 min

Induction cooking heats the pan itself

Engineering and inventions3–5 minAn induction coil uses a changing magnetic field to generate heat in compatible cookware. The choice of pan matters because the heat is not simply conducted from a conventional burner. Explore how the energy reaches the cookware, and why the cooktop surface can still become hot from the pan.

Bicycle gears and the distance of one pedal turn | Speech Topic | speaking.app