Anyone remember these? Anyone have any that were particularly funny?

Would it be some kind of function of the speed at which it was jiggled, or would it be independent of that? Would it decay?

i think we need an actual physicist in here

Sorry to derail, just got excited. Never thought about this before.

>Would it decay?
That's an interesting thought. Intuitively, I think it would make sense, given that it's pretty much a sound wave moving through a dense medium.

I'm probably a retard, though. I can't into physics.

the jiggle travels down the rod as a longitudinal wave at the speed of sound, max, regardless of how hard you jiggle the rod
if you try to jiggle the rod faster than the speed of sound in the rod, the rod will break

the rod is only 'rigid' when talking with distances short enough that a sound wave traveling through the material can cross said distance in a negligible amount of time. In this sense, air is basically rigid when dealing with incredibly small distances, because the speed of sound in air is 343m/s.

Even if you built the most rigid rod in the universe, the speed of sound in the rod could not exceed the speed of light in a vacuum, because the sound wave traveling through the rod does so through layers of particles colliding with each other and those particles cannot move faster than the speed of light.

Source: We used to have this thread all the time three years ago and I have a good fucking memory.

>the rod would bend
What? It's a traverse wave, motherfucker.

longitudinal*

sheeeeeeeiiittttt

>We used to have this thread all the time three years ago
all me haha

>Would it be some kind of function of the speed at which it was jiggled
No, that would be the phase speed (or phase velocity), which isn't relevant to how fast the information travel.

The wavefront will propagate at the group speed, which is the speed of sound. I may be constant or a function of your perturbation frequency spectrum depending on the dispersion relation of the material the rod is made of.

You don't need an "actual physicist" to tell you that, it's all part of undergrad wave mechanics.

>undergrad wave mechanics
I learned that in physics class when i was 12
what fucking education are you paying for?

ah yes the famous middle school wave mechanics classes

Hey thanks, Veeky Forums, learning is the shit!

>physics teacher has a spring
>creates compression and rarefaction in it
>"this is a longitudinal wave. this is how sound works. it's also how seismic waves work. these are not to be confused with transverse waves"
>proceeds to use a rope to make transverse waves
>made me memorize some algebra about nodes or whatever
>get a C on the test because i stayed up all night playing vidya
8th grade, nigga
i'm guessing you grew up in the middle of nowhere

What does any of it has to do with deriving the speed of a wave packet according to the dispersion relation of your material?

in 9th grade we calculated the speed of light in the universe
and then next week we calculated the speed of sound in a spring based on it's hooke constant, and there was something about 'if you compress or stretch the spring too much you fuck it up forever so there's a limit to how fast you can actually actuate the end of the spring to send a sound wave'
I didn't turn in the lab because i was still playing video games all night
it doesn't take a genius to tell you that the critical point where the spring gets fucked up is related to the hooke constant and the dispersion relation of the material
and also it doesn't take a genius to tell you that light traveling through a vacuum is always going to beat a longitudinal wave in a spring in a fucking race

>young enough to remember 9th grade

Mods...

...

>implying you wouldn't need to generate a space hadouken to decelerate from lightspeed to 0

...

But how did you handle the triple integrals?

I wonder if theirs actually a strong enough magnet to pull a 120 poundish human and a small plastic cart?

Wait... what's wrong with this?

Corners still exist

it's not an axiom, thats the problem

limit of the length isn't the length of the limit

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kek r is between centers of mass and thus will never be zero for different objects

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Checkmate, energy conservation fags.

Let's see how retarded Veeky Forums really is.

>wanting to decelerate
no brakes on this train motherfucker

what if you get a ball and a parabola? because the parabolas center of mass exists outside the body, the center of mass of the ball can be laid precisely over that of the parabola

brainlet BTFO
freshmen on suicide watch

if you are inside the object so to say it has to be dealt with differently since the effect isnt comparable to a point masss

for balls it is. are you sure you know about this?

that would be undefined not infinity

what of balls

Right side is pulled down, so less buoyant, negating higher buoyancy of left

the effect of a quantity that decreases quadratically with distance (like gravity) from a point outside a sphere (like any point in the parabola) upon the sphere is equal to what it would be if the sphere was actually a point

>Right side is pulled down
why?

you cant accurately model the parabola as a point the sphere is open season this is for the same reason the equation would misrepresent the nature of the gravitational force exerted by a dyson sphere on an object inside itself if it were reduced to a point but be accurate for an object outside of it

a+b > sqrt(a^2+b^2)

Not him, but I assume he means due to gravity pulling down on the lids.

same thing on the left side

Wait, disregard, had a brain fart, both sides have lids

The movement from the rod would turb into a wave that woukd travel along the rod.

It woukd loose force eventually because of the same resistance within the material.

If it was a perfect material or whatever the wave would travel across the whoke rod and it coukd be used to send a signal, but the speed of the wave is given by the cgaracteristics of the rod, hardness and specific frequency. I'm not that into specific frwquencies and all that but i doubt that a material could be hard enough to transport vibration at the speed of light or higher

...

I mean the right is pulled down towards the stick, making it denser and so less buoyant

>the worry when I can't figure this one out

The strength of the magnet is not the problem. That whole concept is bullshit by default

But the left is pulled down away from the stick, making it more buoyant.

Ignorance is Bliss

Please...

F=(Gmm)/r^2 only works when r>>R

This is baby stuff...

step 5 is intentionally misleading
the 3*$9 subtracts the $3 returned to the kids, not the $2 kept by the friend; so adding $2 is an erroneous step

you can't solve the problem within the framework it gives you b/c it's flawed.

Kids pay you $30, you have $30. You give $5 to your friend, you have $25. The $5 is distributed. Still $30.

Kids pay you $9*3=$27, you have $27. You give $2 to your friend, you have $25.

Relax bro.

>no answer
I consider energy conservation disproven
where is my Nobel prize bitches?

Write up the paper, faggot.

>inb4 "hurrr where's muh funding?!"

I think I can send it to PRL in its current form

when applying infinitesimal approximations, the error should be a higher-order infinitesimal than the approximation, i.e. the ratio of error to approximating infinitesimal should tend to zero. In this case the limit of said ratio at a point on the circle where the tangent to the circle has an angle phi with the horizontal is sin phi +cos phi - 1, which is generally nonzero, so the error is an infinitesimal of the same order as the approximation.

...

there are way more efficient solar thermal generators/techniques than that

Considering that circles don't exist in nature, it is more correct than 3.14.

>free energy

>requires energy from the sun

KYS

Isn't this actually true, you just need an enormous amount of light? Like the kind coming from an evaporating, proton sized black hole?

It's no different than an ion thruster, yet it's mocked while ion thrusters are taken seriously.

its 3*9 - 2 for your bro

it's +2 for him

troll math

You're supposed to subtract the $2 to get $25 right?

5 billion years of sun energy
literally indistinguishable from free energy

You know how, if you leave a cold bottle of water out in the heat, condensation makes water appear around the bottle?

You can use this to create infinite beer. Just leave cold beer bottles out in the heat, more beer will condensate around the bottle ;^)

in the blackboard it should say

(30 - 5) + 3 + 2

or

27 from the kids
>you have 2 of those 27
>while your friend has 25
>the other 3 are owned by the kids

Wait, what's wrong with this?

ITT: people unironically """""correct""""" troll physics

are you retarded?

...

too bad that you'd need an absurdly big piece of paper for this to work

>mfw I took some time to get why it wouldn't work

lolno

you can only fold a paper 8 times

Also paper apparently explodes if you fold it too much.

nice youtube.com/watch?v=KuG_CeEZV6w

Can anyone explain why this happens?

>Problem Archimedes?

I died

because when you fold it, something exponentially

Fuck, I can't stop laughing at this one.

Because a ton of energy and pressure is being internalized within the folding paper, and the paper can't hold all of the energy within, so it just lets it all out (explosion). This is just a brainlet's guess.

you're telling me that a 1000x1000km(for example) sheet of paper with 0.1 mm thickness wont fold more than 7 times? that doesn't sound right

world record is 13

Isn't this just the Hyperloop?

but what size of paper did they use?

30km

I'm pretty sure it will, but that is an edge case. Regardless however, I do imagine that it would still eventually reach the point where you can no longer fold it without catastrophic failure.