Physics

Hippalectryon

Jul 14, 2016 13:54

@Chinatsu-creepy-chan I may be able to help :D

Chinatsu-creepy-chan

wait @arda, there's Pokemon GO to Windows Phone?

Memor-X

@ToshinouKyouko the japanese have already mastered that

Train Pushers At Work

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arda

I use Android now

Toshinou Kyouko

:D

same, i switched recently

Chinatsu-creepy-chan

@Hippalectryon do you know how inertial forces appear?

Toshinou Kyouko

Jul 14, 2016 13:55

just in time for PoGo :)

Chinatsu-creepy-chan

like, I'm with problems when talking about a corpse without friction in a rotating disk (centrifugal force)

Inertia Force calculation in a Reciprocating Engine _ Graphical method

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@arda D:

I'm all alone now

Hippalectryon

@Chinatsu-creepy-chan yeah I know that stuff

Not sure about the video's method though - is it important ?

Chinatsu-creepy-chan

not at all

I'm looking for a way to ~be~ the observator

I saw that you'd simply do some line integrals in Wikipedia

But I did not get the idea

arda

Yay physics

Taisho

4

Memor-X

Jul 14, 2016 13:59

@Taisho what

Taisho

https://www.google.com/searchbyimage?image_url=http://googledrive.com/host/0B9du34AejghtVkpSaDVKQ1BqWnc/5d6776d77615fe616df0a5ee2545425c_thumb.png | http://tineye.com/search?url=http://googledrive.com/host/0B9du34AejghtVkpSaDVKQ1BqWnc/5d6776d77615fe616df0a5ee2545425c_thumb.png | http://saucenao.com/search.php?url=http://googledrive.com/host/0B9du34AejghtVkpSaDVKQ1BqWnc/5d6776d77615fe616df0a5ee2545425c_thumb.png | http://iqdb.org/?url=http://googledrive.com/host/0B9du34AejghtVkpSaDVKQ1BqWnc/5d6776d77615fe616df0a5ee2545425c_thumb.png

Chinatsu-creepy-chan

@arda irony? D:

Hippalectryon

Not sure what you mean by "being" the observator, can you be more specific ? Maybe we didn't learn the notions the same way @Chinatsu-creepy-chan

Memor-X

@Taisho makes me think of Homicide Jack

or was it Genocide Jack

Chinatsu-creepy-chan

@Hippalectryon the observator accelerates/moves in time

So all the space "moves" for him

holy f*

Rotating reference frame

A rotating frame of reference is a special case of a non-inertial reference frame that is rotating relative to an inertial reference frame. An everyday example of a rotating reference frame is the surface of the Earth. (This article considers only frames rotating about a fixed axis. For more general rotations, see Euler angles.) == Fictitious forces == All non-inertial reference frames exhibit fictitious forces. Rotating reference frames are characterized by three fictitious forces: the centrifugal force, the Coriolis force, and, for non-uniformly rotating reference frames, the Euler for...

Hippalectryon

Jul 14, 2016 14:03

Oh so you have a galilean frame, and then around him you have another frame which is the operator's frame, a priori non galilean and thus subject to inertial forces in the observator's referential ?

(galilean frame = inertial frame for me)

arda

@Chinatsu-creepy-chan nah I love physics

Chinatsu-creepy-chan

Wow that's a weird way to put it up but

meh IDK

I don't have a teacher to teach me these things so I'm all confused

Hippalectryon

If the observator "moves", it has to be relative to a special frame, not his. The observator is immobile in his own frame

Well anyway, I'm not sure I grasp what your question is exactly

Chinatsu-creepy-chan

Oh yeah, I got you

Hippalectryon

7 mins ago, by Chinatsu-creepy-chan

I'm looking for a way to ~be~ the observator

Sakamoto

Jul 14, 2016 14:06

0

Q: Can a transformed saiyan lower his ki to base-human level when transformed?

In Dragon Ball Resurrection of Freezer , Goku when transformed in Super Saiyan God Super Saiyan is almost killed by a laser beam from Sorbet . Now how could this happen? Was his ki so low even when he was a SSGSS? Later in the Dragon Ball Super series this seems to be corrected because he isnt tr...

dragon-ball-z

Chinatsu-creepy-chan

The observator moves relative to the inertial frame of reference

Hippalectryon

Indeed. What's preventing you from "being" the observator ?

Chinatsu-creepy-chan

@Hippalectryon eeeh, IDK

That's what I thought:

The observator moves with an s (space) equation so the world has to move, to him, with an s^-1 equation (inverse function)

I want a really sad anime

Is EVA good 'n sad?

Hippalectryon

@Chinatsu-creepy-chan That's true

@Chinatsu-creepy-chan You've already watched 5cm/s ?

Chinatsu-creepy-chan

Jul 14, 2016 14:24

@Hippalectryon nope. It's a move isn't it?

Hippalectryon

A movie in three parts

myanimelist.net/anime/1689/Byousoku_5_Centimeter

There's also Haibane Renmei which I haven't watched yet (PTW) but looked primising

Chinatsu-creepy-chan

@Hippalectryon centrifugal force will only appear in a punctual corpse if there's friction, right?

@Hippalectryon noice

Hippalectryon

@Chinatsu-creepy-chan Oh no it's totally unrelated

Chinatsu-creepy-chan

But the motion is parallel to the corpse..

Hippalectryon

When moving around an axis, you'll undergo a centrifugal force wether there is friction or not

How can the motion be parallel to the corpse if the corpse is punctual ?

Chinatsu-creepy-chan

Jul 14, 2016 14:34

KEK

I'm stupid LOL

But how would it even move?

A punctual body over a rotating 2d circumference

Hippalectryon

Electromagnetic forces for instance ?

Think of a charge in a magnetic field perpendicular to its initial speed

(well then the rotating thing doesn't play any role uh)

If it moves because of the rotating circumference then yeah you'll need friction (unless you use some induction shenanigans for instance)

But you don't need a rotating plate to induce a circular movement

Taisho

2

Chinatsu-creepy-chan

Jul 14, 2016 14:49

@Hippalectryon IKR, the body can move by itself

that was one of the main questions I had

If there's a guy with ultra-slippery shoes in a rotating circumference, then he would just stay in the same place right?

Hippalectryon

Yep

Well he'd fall but that's another story :P

Chinatsu-creepy-chan

Ok, I got that. Yay :D

So, can you give me an example of centrifugal force plz? I can't imagine one without friction (the corpse would just move by itself in regular motion so he wouldn't be thrown out because of inertia)

Hippalectryon

@Chinatsu-creepy-chan Well for an easy example : take the earth orbiting around the sun. In the sun's (quasi inertial) reference frame, the earth is subject to the gravitational force. In the earth's reference frame, the only 'newtonian' force the earth is subject to is a gravitational force from the sun, and thus it should move, which is absurd (the earth is immobile in its own reference frame).

Hopefully since the earth's reference frame is not inertial, there exists a centrifugal force to counter the effect of the gravitational force.

Chinatsu-creepy-chan

@Hippalectryon I don't get this at all..

What should move? The Earth? The Sun?

Oh. The Sun should move... heh

Hippalectryon

Ah no the sun is immobile in this case (take it has having a huuuuuge mass)

Ok so let's look at the second part of what I said.

We're studying the earth's movement it its own reference frame, in circular translation around the sun

Chinatsu-creepy-chan

Jul 14, 2016 15:00

@Hippalectryon I mean, the sun "moves" in relation to the earth.

Hippalectryon

What does Newton's 2nd law tell us about the Earth's movement in its own referential ?

@Chinatsu-creepy-chan ah yes

Chinatsu-creepy-chan

@Hippalectryon 2nd law? F = ma?

Hippalectryon

Yep. What's F a more explicit way ?

Chinatsu-creepy-chan

Interaction

@Gao ouch...

Hippalectryon

Well it's the sum of all the forces exerced on the Earth right ? (assuming it's a pointmass)

Chinatsu-creepy-chan

Jul 14, 2016 15:12

@Hippalectryon yup

Hippalectryon

Ok. What are the forces in this special case ?

Chinatsu-creepy-chan

Eh... Gravitational and, like, internal forces that we won't consider? u_u

Hippalectryon

Ok. So we have a=F_grav/m right ?

Chinatsu-creepy-chan

Yes

Hippalectryon

So a=/=0 ? But aren't we in the earth's own frame ? How is that possible ?

Chinatsu-creepy-chan

Jul 14, 2016 15:16

@Hippalectryon I don't get this.

You mean, earth "shouldn't" be moving?

Hippalectryon

Earth is moving, say, in respect to the sun's center. But earth isn't moving with respect to its own center is it ?

In Earth's reference frame, Earth is always in the center of the frame, with coordinates (0,0,0)

Chinatsu-creepy-chan

Oooooooh.

( ͡° ͜ʖ ͡°)

Hippalectryon

So, where's the catch ? :D Why is the acceleration nonzero in the Earth's reference frame ?

Chinatsu-creepy-chan

@Hippalectryon Fictious force?

Hippalectryon

When is Newton's second law valid ? What are the conditions ?

Chinatsu-creepy-chan

Jul 14, 2016 15:28

tbh, IDK

Hippalectryon

Newton's second law is only valid in intertial frames

And the earth's frame isn't an inertial frame since it's rotating around the sun's frame, which is supposed to be inertial

For all non-inertial frames, for Newton's second law to be valid you need to add the inertial forces in ma=F => ma=F+F_inertial

Chinatsu-creepy-chan

AAAAAH

I'M SO DUMB

It's so obvious, like

a moving train with speed v and a guy running with speed -v: he'd just be in the same position

Thank yooou <3<3<3

Hippalectryon

And if you actually write the formula for the inertial force, you'll realize that it's the exact opposite of the gravitational force

:-)

Taisho

Chinatsu-creepy-chan

@Hippalectryon What is its formula?

It was going to be my next question :P

Hippalectryon

Jul 14, 2016 15:36

Do you know the formula for the centrifugal force for an object rotating around an axis ?

Chinatsu-creepy-chan

yup, mv²/r (non accelerated motion)

Hippalectryon

Yep. Now any way to express v in function of G,mass_sun ? (G is the constant that appears in the gravitational force)

Chinatsu-creepy-chan

Since F = GMm/r² and g = GM/r²

$v = \int \frac{GM}{s^2}\, \mathrm{dt}$

(use chatjax)

Hippalectryon

Well that's not false but it's not very useful

Do you know that the acceleration of an object rotating at a constant speed $v$ and radius $r$ is $a=v^2/r$ oriented towards the center ?

(in the center's inertial frame)

Planet Express Delivery

Jul 14, 2016 15:54

0

Q: Translation of anime soundtrack lyrics

These are the lyrics of a Japanese song (OST from 'Katanagatari' anime series). I understand that it is about killings and revenge from google translate, but the translation is not accurate and not at all helpfull. たがぬこえひびぬこえたがぬなきひびぬなきたがごとにみたまうちあがつみにさばかれんあらさかのかみのおのいのちなむほのをたつま...

song-lyrics anime

Chinatsu-creepy-chan

Jul 14, 2016 16:20

@Hippalectryon Yeah

(my bad, just had lunch)

Hippalectryon

Alright so if we look at the Earth's movement in the sun's inertial frame, what relation does Newton's second law give us between $v$ and $G,r,M_{sun}$ ?

Chinatsu-creepy-chan

@Hippalectryon I don't get this...

Hippalectryon

@Chinatsu-creepy-chan Write Newton's second law for the earth in the sun's frame. Since the sun's frame us by hypothesis inertial, the only force to consider here is the gravitational force.

Chinatsu-creepy-chan

Jul 14, 2016 16:54

Ok...

F = ma = GM/r²

Hippalectryon

now substitute $a$ by

1 hour ago, by Chinatsu-creepy-chan

yup, mv²/r (non accelerated motion)

Chinatsu-creepy-chan

mv²/r = GM/r² -> v = root(GMr/m)

Hippalectryon

m isn't squared

finally express $v$ in function of $M,G,r$ and compare the gravitational force and the inertial force

Chinatsu-creepy-chan

oh, you're right

Maid Café (メイド喫茶)

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