Back to topics

Why does one pedal turn take you different distances?

Changing bicycle gears changes the relationship between your pedals and the rear wheel. The teeth on the chainring and sprocket help explain why the same turn of the pedals can produce a different distance along the road.

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?

Start reading

Ready to try your ideas aloud?

Your topic carries over. Record up to 2½ minutes, depending on your plan.

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.

12–15 min

How GPS finds you, and fixes its clock

Engineering and inventions12–15 minYour 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.

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

Engineering and inventions8–10 minA 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.

Engineering and inventions

How can an induction cooktop heat the pan itself?

An induction cooktop can heat compatible cookware without first making an element glow. A changing magnetic field transfers energy into the pan, making the choice of cookware part of how the system works.

3–5 min

How can an induction cooktop heat the pan itself?

Engineering and inventions3–5 minAn induction cooktop can heat compatible cookware without first making an element glow. A changing magnetic field transfers energy into the pan, making the choice of cookware part of how the system works.

Why does one pedal turn take you different distances? | Speech Topic | speaking.app