Hacker News new | past | comments | ask | show | jobs | submit login

>For drones, I like to ask: "how do you think the drone moves forward?" [over power the rear two, underpower the front]

Careful - this explanation isn't just a simplification - it's outright wrong. Applying differential power to the front and rear rotors is how you initiate a pitch moment. You must reverse the pitch moment when the drone is at the desired attitude. This attitude may cause the drone to accelerate in a given direction. When the drone has reached the desired speed the attitude change must also be undone (but not completely, due to drag) to kill the acceleration. So to bring a drone from a hover to a steady forward velocity requires four applications of differential power - two one way, and two the other way. It's not even true that the rear ones expend more total power over the course of the maneuver - it's symmetrical.

It's a neat example of Newton's First law, and also a good opportunity to explore a little about 0-order, 1-order, 2-order motion (you might explore what kicking your foot does when 1) walking 2) riding a skateboard, 3) driving a car). But if you think it's too complicated, better to avoid it entirely than give the wrong idea.

(A related question you can ask - when an airplane is in a steady climb, which is greater - the lift on the wings, or the weight of the plane? Answer: they are the same! Otherwise the aircraft would be accelerating up or down.)




Correct. BUT, I've found this level of detail is often too much for a 5 to 6th grade level audience.

So I usually start with "what if the back rotors go a little faster?": it tips it forward, beginning a series of operations leading forward motion (like turning the wheel of a car away from center -- what happens if you keep it turned?)

I've also found that words matter: "attitude", "differential", "pitch", "velocity", "acceleration", etc. -- may be hard to access, and simpler terms like "faster", "slower", "speed", "tipped" are usually more broadly understood.


Spot on! The level of explanation and the intent behind the explanation hugely matter. An explanation that is correct but becomes inaccessible can become a demotivator for kids (not for all kids). An explanation that makes things too mundane can cause a consequent lack of curiosity.

A recent such explanation episode got me thinking more about this - I'd recently got a pair of noise cancelling headphones and wanted to demo it to my kids. In an inspired (or dumb) moment, I introduced it to them like this - "you know headphones play music right, this one plays silence." I'd like to think I caught a whif of both understanding and "what the .." in their expressions :D




Guidelines | FAQ | Support | API | Security | Lists | Bookmarklet | Legal | Apply to YC | Contact

Search: