Haalp, o physics geeks on the flist

[snowgrouse]

HAAALP. What's the name for that point where a pendulum reaches the end of its trajectory, when it's swung as high as it can go before it starts moving back? I was reading Wikipedia on it and scratching my head. They talk about the "moment of inertia", but apparently that can also mean the movement itself if it just keeps doing the exact same thing

Comments

[astrogirl2]

I think "the end of its trajectory" is fine, actually. Terms like "apogee," "apex" and "critical point," however, are kind of wrong. Especially "apogee." :)

To be honest, I don't actually remember calling it anything back when I was studying this stuff. I think we usually just described it with equations. :)

[snowgrouse]

Thank you! That helps muchly.

[astrogirl2]

It might not bother most people when used metaphorically, but in this case it definitely reads as wrong to me, and would very possibly ping my "wait, this person doesn't actually know what they're talking about" detector and throw me out of the story. *shrug* "Apogee" is a technical term. It is, indeed, the point of highest potential energy, but it's not the term for any point of highest potential energy, only that of an object in orbit around the Earth. (Technically, it's not even the correct term if you're orbiting something other than Earth.)

"End of its trajectory" isn't exactly scientifically precise, but it doesn't ping my "misuse of a technical term" detectors in the same way.

Other space geeks' mileage may vary, of course. :)

Anyway, there are lots of ways to describe that particular point, it's just that I can't think of any that aren't pretty clunky and non-poetic. "Point of maximum displacement," for example.

[ushas42]

My dictionary defines Apogee as:

1. (astronomy) The point in the orbit of the moon or a satellite at which it is furthest from the earth. The opposite of Perigee.

2. (figurative) The highest point in the development of something; the climax or culmination of something.

Sounds like it would work fine as either a scientific term or a metaphor.

[astrogirl2]

Yeah, you can use it as a metaphor -- "His career had reached its apogee" -- but using it to describe a pendulum is really mixing the physics metaphors in a way that's not gonna work to someone who understands physics.

Or such is my take on it, anyway.

[lordavon]

I have to agree -- if we were talking about a space elevator, we might stretch the metaphor, but otherwise, apogee really only refers to orbital objects.

I seem to recall there is a real term for that moment of highest point in the arc, but damned if I can think of it. And my physics books are in NJ. (And somehow I think my metaphysics books aren't going to help -- most of them are on time travel anyways.)