NeatNit
@NeatNit@discuss.tchncs.de
- Comment on Hey jackass, this is why trucks with large tires are supposed to have mud flaps. 1 day ago:
If no one’s gonna mention it, I will: love the Pikachu plush! my mom also has some plishies on her windshield, it always gives a cozy feeling 😊
- Comment on Which is it Lemmy? 6 days ago:
So we might think: a cube falling through a floor portal and flying out another floor portal right next to it, kinda looks like how a bouncy ball bounces off the floor, and should apply forces on the floor similar to that - an elastic collision. Unfortunately, this brings us right back to conservation of momentum, which didn’t work out. But maybe I just did it wrong? Maybe, if done more carefully, conservation of momentum can work without being dependent on the reference frame?
I genuinely don’t know yet. Time to bring out the calculus.
We have:
M = the mass attached to the portal (e.g. the floor)
V = the velocity of M
V’ = dV/dt = the acceleration of M (assuming no other forces)
F = MV’ = the force applied on the portal
m’ = dm/dt = the rate of mass entering the portal
v = the velocity of the mass entering the portal
If we assume conservation of momentum (our old nemesis), the force applied on the portal should be the same as the momentum taken from the mass entering the portal:
F = m’v
But now we’re back to the case from before, where the choice of reference frame changes the outcome! We’re not having that. So I hereby decree:
The force applied upon a portal by a mass entering it must be calculated by conservation of momentum in the intertial reference frame of the portal itself at the instant under examination.
This gives us, effectively: F = m’(v-V)
Now THAT’S something we can work with!
Note that this formula also works for the exit portal. In that case, m’ is negative.
A curious result follows.
For the entry portal, m’ is positive, and (v-V) is a vector pointing into the portal. (This must be the case, otherwise the mass would be exiting the portal). Therefore, the force would be pushing the portal into the wall.
For the exit portal, m’ is negative, and (v-V) points out of the portal, therefore the portal again would be pushed into the wall.
The result: whenever anything passes through a portal, both ends always get pushed in the same direction.
So, back to my thought experiment.
If a portal attached to a free-falling panel falls onto a cube, the cube’s entry into it would brake its fall to some extent. However, this wouldn’t be the only force in play.
As I said in my previous comment, forces applied between the two halves of an object going through a portal, get applied to the portal itself. In practice, this mostly means tension and compression forces. In the static analysis from before, it was compression.
As the panel is falling onto the cube, a part of the cube is already out the other side and moving away the portal. If the panel has slowed, this would apply a pulling force (tension) on the part of the cube that still hasn’t made it in. This tension force actually compels the portal, and the panel it’s attached to, to speed up towards the ground.
So, in total, would the panel be slowed, accelerated, or unaffected? Maybe the forces cancel out and it just continues on its normal freefall? I don’t know yet. Would need to do more math.
- Comment on Which is it Lemmy? 6 days ago:
Okay, after thinking about this a while, I’ve decided that conservation of momentum just doesn’t work, unless the portal actually absorbs the mass of every object passing through it, which would probably cause its own set of contradictions.
Instead, I think forces that act through the portal are applied to the portal. What do I mean by this? Well, take this classic case of a cube floating halfway through two floor portals:
____ ____ | | | | ___++++++++++______----------___
(sorry, can’t do better than ASCII art right now)
The system has reached equilibrium, and nothing is moving. Both halves of the cube are being pulled down by gravity, but cancel each other out by applying a normal force on each other right at the portal interface. What I’m claiming is that this normal force is applied to the portals, which ultimately transfer it to the floor. If this entire floor was a scale, it would measure the calibrated weight of the Weighted Storage Cube.
But this is the static analysis. What happens when objects are in motion? To be continued…
- Comment on Which is it Lemmy? 6 days ago:
The answer is definitely B (see other comments), but I think the more interesting question is, how does it affect the portals themselves and the surfaces they’re attached to?
When the portals are attached to a solid unmovable wall (as in the games), we can pretty much ignore the forces acting upon the wall as they will just be automatically cancelled out by the normal force. But the same does not apply for portals attached to detached panels. Let’s say that instead of a piston pushing down, the portal is attached a free-falling panel with the portal facing down.
We are inclined to assume that as the portal falls onto the cube, it feels no force, as if it fell through air or through a vacuum. But is that really the case? Maybe instead, the falling portal experiences resistance from the cube? Or even, actually, an accelerating force?
Let’s assume conservation of momentum at each end of the portal. That is, in the general case: if the portal (which we assume has no mass) is attached to an object with mass M and velocity V, and “swallows” a cube or other object with mass m and velocity v, and at the end of this interaction the portal-surface object with mass M has velocity V’, then we expect:
M × V’ = (M × V) + (m × v)
Mass is not conserved because the cube was transferred to the other portal.
Solve for V’:
V’ = V + (m/M) v
This is a strange result. The cube’s momentum is imparted into the portal, but the result would be different depending on our reference frame. From a reference frame tracking the cube pre-interaction, v = 0 (by definition) and so V’ = V, the portal-surface object has no change in velocity. But in any other reference frame, it does.
Physics can’t be affected by reference frame (thanks, relativity) so this analysis must be wrong.
… I’ll keep thinking on this.
- Comment on Which is it Lemmy? 6 days ago:
The “ragebait answers only” in the OP is the only thing stopping me from actually raging at everyone saying A. I am giving them all the benefit of the doubt, they’re deliberately saying the wrong answer.
Everyone saying B missed the assignment and answered accurately.
- Comment on Which is it Lemmy? 6 days ago:
Now there’s a high quality ragebait answer
- Comment on Repeating of course 1 week ago:
They are fractions of the format m/(2^n), but they only mimic fractions like 2/5.
- Comment on Goodnight Punpun creator Inio Asano says the manga scene’s attitude towards AI is one of the reasons he put Mujina Into the Deep on hiatus - AUTOMATON WEST 1 week ago:
This is the relevant quote:
“In the current state of things, mangaka are not allowed to use AI. But using AI actually drives up the quality by a mile. So doesn’t that mean it would be best to not draw the manga now? Maybe they suddenly lift the ban [on AI] next year, so it might be better to start drawing after that happens. I’m currently on standby in that sense,” Asano says. Though he didn’t elaborate if or to what extent he hypothetically plans to use AI, he said that using it could significantly speed up the modeling process.
- Comment on Is this a rope hanging under a helicopter? 2 weeks ago:
Personally, I just don’t like the guy and his vibes. But I wouldn’t tell random people online to avoid him, he’s not that bad.
There was also that self-driving car video which turned out to be really scummy.
- Comment on Is this a rope hanging under a helicopter? 2 weeks ago:
I commend you for making it this far on the internet without encountering it.
- Comment on [deleted] 2 weeks ago:
There is some benefit to this in some cases: they compete with the others of their species for the same finite set of resources, causing fewer breeders to make offspring. They might also attempt to breed with a fertile mate (unsuccessfully), causing that mate to never produce offspring when they otherwise would have.
The effectiveness of this is obviously very dependent on the species and their breeding habits, and I know nothing about this one. I’m just talking about the general case.
- Comment on [deleted] 2 weeks ago:
Explanation? What is that thing?
- Comment on 4 weeks ago:
Watched Avatar: The Last Airbender with Hebrew subtitles, there were loads of mistranslations. Sometimes stating the exact opposite of what the English original said, other times the transistor just completely doesn’t understand what they’re translating and results in random nonsense statements. Sorry I don’t have any specific examples, but really it’s too common.
Lest you think it’s because it’s a kids show: more recently I’ve been watching Shakespeare & Hathaway: Private Investigators with my mom (a British cosy mystery comedy-drama television series, thanks Wikipedia), and mistranslations in the subtitles are just as common.
It really makes me worry about how common similar mistakes could be in e.g. Japanese content (anime, video games) subbed to English. I don’t know any Japanese, so my ONLY source of information is the English sub, and if it’s as flaky as the Hebrew subs for English sources, I really could be missing out :(
- Comment on Why do tires have the width and diameter they do? 4 weeks ago:
When the vehicle weight increases while tire PSI stays the same, the contact patch (area squished flat against the pavement) increases in size.
If the vehicle gets heavier, doesn’t the tire pressure increase?
- Comment on 4 weeks ago:
I know this! youtu.be/ztHq1NLEbio?t=9m4s (note the timestamp, 9:04)
Short version: surprisingly, yes!
- Comment on courier transform 4 weeks ago:
Not only that, it’s its own inverse (besides some constants), so you just need to apply the same transform again to get back the original.
I don’t remember which one it is though, so it could be either. Odds are 50/50, right? So all you have to do is mail yourself the very expensive item that got superficially damaged in transit, and there’s a 50% chance you’ll get it back good as new!
- Comment on Scan to Verify You're Human 5 weeks ago:
… what?
- Comment on How do you distance yourself from your country when it doesn't represent your views anymore so you won't be viewed by the rest of the world as part of the problem? 1 month ago:
Yeah, to say the least. A year or so before the October 7th that sparked our country’s intentional relations nosedive, there were massive country-wide protests, which I also participated in. You can probably find articles about it. It was protesting against certain anti-democratic things the government was doing (I don’t want to get into the weeds here), but it was also fueled by unprecedented distrust of just about everyone in the government, and most of all Netanyahu. This distrust has only gotten worse.
That bastard should be in jail, but as “luck” would have it, he is always so preoccupied with all the wars he started that he can’t attend his court trial where he faces serious criminal charges. What’s that? Conflict of interest? He gains personal benefit from neverending war, so he has no incentive to actually end it (be it through diplomacy or through military victory)? Nah, I’m sure he has the country’s best interests at heart.
That people keep voting for him astounds me. But we’re seeing similar patterns worldwide, most obvious example being USA, so I guess this democracy thing is just failing all over the place this decade.
- Comment on Is there a parenthesis gesture like there are air quotes? 1 month ago:
Noooooo stop educating me against my will!!!
- Comment on How do you distance yourself from your country when it doesn't represent your views anymore so you won't be viewed by the rest of the world as part of the problem? 1 month ago:
Speaking as an Israeli, I don’t have an answer for you. But you’re not alone. Most of the people I know are in the same boat to various extents. That tends to happen with today’s social-media-fueled political polarization.
What I try to say online (if it comes up and becomes a problem) is this is just where I was born. But to be honest, I find that most people worth talking to don’t give a shit where you live. As one of them once told me in reply, you don’t control your spawn point.
- Comment on Is coding possible on smart phones ? 1 month ago:
I highly recommend Unexpected Keyboard for things like that. I still wouldn’t want to do more though, it’s just not comfortable.
github.com/Julow/Unexpected-Keyboard (F-Droid / Play Store)
- Comment on Is there a parenthesis gesture like there are air quotes? 1 month ago:
You might be onto something.
- Comment on Is there a parenthesis gesture like there are air quotes? 1 month ago:
I like it!
- Comment on Is there a parenthesis gesture like there are air quotes? 1 month ago:
Air quotes almost never mean literally quoting someone else. I’d say it signifies that the speaker doesn’t agree with the words they are saying. Per Wikipedia: “Air quotes are often used to express satire, sarcasm, irony or euphemism and are analogous to scare quotes in print.”
- Submitted 1 month ago to [deleted] | 16 comments
- Comment on $1$ 1 month ago:
There have been some claims that the numberphile video is very misrepresentative of the underlying math. But I never dug deep enough into it.
- Comment on [deleted] 1 month ago:
In many languages the days are numbered, e.g. “First day”, “Second day”, …, “Seventh day”. Speakers of those languages have no question about when the week starts.
en.wikipedia.org/…/Names_of_the_days_of_the_week#…
Notably, the older languages start the week on Sunday. Some of the languages that start the week on Monday can be attributed to mistranslation from the former group. So starting the week on Sunday is historically more correct.
Disclosure: I speak a language that starts the week on Sunday, so I’m biased.
- Comment on Handy tip 2 months ago:
Literal superpower. You hold us all at your mercy.
- Comment on Handy tip 2 months ago:
Is it worth it? That depends. What percentage of the boys does it bring to the yard?
- Comment on Handy tip 2 months ago:
Yes. In a frictionless vacuum.
