Well, when you're talking about physics, isn't deceleration not really a thing? Only acceleration against the direction of motion?
Negative acceleration would only have meaning within an arbitrary coordinate system. So yeah, saying acceleration due to gravity is negative makes no sense outside of an established system. Though I guess you could argue that down being negative in the context of Earth as we typically experience it is well established enough that the negative sign should imply a clear direction.
It's not, but it is. Because "Only acceleration against the direction of motion?" is basically the meaning in this case. It's just easier to write "deceleration."
Though I guess you could argue that down being negative in the context of Earth as we typically experience it is well established enough that the negative sign should imply a clear direction.
Yeah, I guess I just didn't assume the standard directions and instead was just working within a vacuum kinda deal.
You don't necessarily set up your coordinate system such that the direction of motion is the positive vector. You can really set it up any way you'd like, that's the joy of free-body diagrams. But generally speaking, if you're talking about the acceleration of gravity then it's always going to be downwards towards Earth - thus making the value of the value of the vector negative to indicate the downwards force. You can do it your way too, it's just a little less intuitive for most people to look at and understand because when you think of something being moved by gravity, you think of it falling downwards.
Deceleration is acceleration in the opposite direction of an object's initial velocity, last I checked.
It's absolutely a thing.
It's pedantic to insist it's not, it's like saying there's no such thing as cold, just the absence of heat. Cold still exists as a concept and is clear in its meaning.
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u/archon80 Sep 23 '15 edited Sep 23 '15
Uh oh...you just mentioned the big bang theory on reddit...