So you need to Pick a problem: keep an elevator from falling

You're in a metal box, hanging over a ten-story drop.

1. So it hangs from six steel ropes, and any one could hold the car alone.
2. But a full car is heavy, and hauling it up takes a huge motor.
3. So the ropes run over a wheel to a counterweight, so the motor only lifts the difference.
4. But what if the car ever ran too fast?
5. So a governor trips a clamp, and the safety gear jams wedges against the guide rails until the car stops.
6. And buffers wait in the pit, and door interlocks won't let it move until every door is locked.

You're not hanging by a thread. You're hanging by six.