Watch these recommended TED-Ed Lessons

Why don't perpetual motion machines ever work?
Perpetual motion machines — devices that can do work indefinitely without any external energy source — have captured many inventors’ imaginations because they could totally transform our relationship with energy. There’s just one problem: they don’t work. Why not? Netta Schramm describes the pitfalls of perpetual motion machines.

The mystery of motion sickness
Although one third of the population suffers from motion sickness, scientists aren’t exactly sure what causes it. Like the common cold, it's a seemingly simple problem that's still without a cure. And if you think it's bad on a long family car ride, imagine being a motion sick astronaut! Rose Eveleth explains what’s happening in our bodies when we get the car sick blues.


Additional references

How roller coasters work - How Stuff Works
Roller coasters give riders the experience of flying as they shoot riders down long stretches of spiraled tracks. But what about “that sinking feeling”? Find out why it occurs.

Hydraulics - Britannica
Hydraulics, branch of science concerned with the practical applications of fluids, primarily liquids, in motion. Find out more about how hydraulics extends to such mechanical devices as fans and gas turbines and to pneumatic control systems.

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