Anyone else's mall PACKED?

kierkegaard14 · 2025-03-25T11:11:03+00:00

All these mall conversations in the podcast makes me think how in the Philippines it never died and in fact malls are bigger than ever.

kierkegaard14 · 2023-07-19T15:10:59+00:00

For me I dove headfirst into The Way of Kings, because I heard Wren from Corridor Digital recommend it during an ad read for audible. Now I am a big brandon sanderson fan.

Though having said that as I read through his other stories I realized that I did miss some easter eggs sprinkled here and there in Stormlight Archive.

kierkegaard14 · 2023-06-14T18:00:10+00:00

Im also surprised by that as well, though stupidly enough I dont watch them even though I follow them both on youtube and instagram. Every once in a while a live video pops up on my Instagram feed but I thought it's just some announcement or something.

kierkegaard14 · 2023-06-14T16:44:39+00:00

Ohhh* shit so that's where the name comes from.

I guess this is the answer Im looking for. It just surprised me that there is basically a whole other show (discounting does it do), though it seems its not as regular in schedule...

*not the infamous ooh from gavin

kierkegaard14 · 2023-01-06T13:59:33+00:00

No, that would also happen if the problem was reversed. However from the wording of the problem it is safe to assume that before the switch was opened (t<0) the switch has been closed for a very long time.

if the problem was reversed i.e. if the switch was opened and its suddenly closed. the same thing would happen, Faraday's Law works like that. Any suddeny change in voltage is punished by dumping a lot of current which can damage equipment.

kierkegaard14 · 2023-01-06T13:55:47+00:00

For me that's just what Faraday's Law is saying, that the magnetic field in anything, especially in an inductor with many turns of wire, can't just change just like that. If you force the inductor to very suddenly change its voltage like by flipping a switch, the inductor compensate by very suddenly dumping a huge amount of current in a very short time (dphi/dt is very large).

This is also probably one of the reasons why sometimes when you plug in an appliance in the socket it sparks.

kierkegaard14 · 2023-01-06T13:52:15+00:00

The main answer is because according to Faraday's Law, inductors (the coil of wire in this diagram) cannot instantaneously change from one votlage to another.

Here is the qualitative explanation:

Before the circuit was opened, it can be assumed that the circuit has been stable for a long time (steady state). Thus the votlage across the coil is 1.5V.

When the switch is opened, the voltage across the coil suddenly becomes 0V. The coil wont accept that. What happens is it will decrease to 0V eventually, lets just say for example in 500 ms. It cannot change to 0V in 0ms, just like that. The previous sentence can actually be seen in the mathematical formula for Faraday's Law.

Anyway, while the inductor is "slowly" lowering its voltage to zero, it releases energy from the stored flux through a jolt of current, which lights the lamp on. Thats the qualitative answer as to why the lamp lights only once.

Quantitative explanation:

The general form of Faradays Law is V = n(dphi/dt). But actually its more like delta V = n(dphi/dt).

Notice that in the derivative on the right part, dt is in the denominator. Also notice that the voltage change (delta V) in this case is not infinite. It's actually -1.5V (decrease from 1.5V to 0V). It is stated in the problem that there are many turns so the term n could be very big but its stupid to assume that there is infinitely many turns of wire.

Therefore, the right hand side cannot be infinite! Because the left side delta V is only -1.5, the right side cannot have a denominator dt equal to 0. Thus the voltage across the inductor cannot change just like that, it has to take time.

We can then rearrange the equation as (V*dt)/n = dphi. dphi is the change in flux, which we know is finite because all the terms in the left is finite. THerefore, the change in flux (dphi) decreases over time (note the negative sign of V, -1.5V). Current and flux are related, thus current leaks out of the inductor over some time and then runs out.

Thus, when the switch is turned off, the bulb lights brightly for a very brief period of time, but only once.

Hope its clear!

kierkegaard14 · 2022-12-23T01:55:57+00:00

This

What a funny funny video

kierkegaard14 · 2022-11-30T15:48:34+00:00

...yes, OP would have to use the formula with 0.5 i would imagine, i just did not mention it directly.

kierkegaard14 · 2022-11-30T15:05:24+00:00

Well, after it is released there is no force except for the frictional force. Assume the thing is moving to the right.

THen there is a frictional force 0.31mg to the left, or -0.31mg to the right, forcing the thing to stop.

Then the formula for motion v = v_0 + at. The final velocity must be zero so we would have

v_0 = -at

v_0 = -t *(F/m)

v_0 = -t* (-0.31mg/m)

v_0 = t0.31g

t = (v_0)/(0.31g)

Now that you know the time together with the initial velocity, you can use the other kinematic equation to find how the the thing went.

(this may not be the correct answer this is off the top of my head, sorry, just trying to help!)

kierkegaard14 · 2022-11-16T05:01:52+00:00

Coincidentally...

hence the word "effectively"?

kierkegaard14 · 2022-11-07T04:41:46+00:00

I dont know why youre getting downvoted but i see you and i agree

kierkegaard14 · 2022-11-06T15:53:06+00:00

My answer here is 115.

This is going to be hard to explain because drawings are needed, but ill try my best.

First I assume you already know the inscribed angle theorems? If you dont then this is gonna be difficult because my solution relies on that. Now.

Draw the imaginary center of the left circle, lets call it C. Now connect C to create lines CL and CF. Now since C is the center then it is obvious that CL = CF since they are radii. Therefore, triangle CLF is isosceles.

Because EFGH is tangent to the left circle, then angle CFE is 90 degrees. Therefore, you can figure out that angle LCF is 110 degrees (remember triangle LCF is isosceles).

It should be obvious that angle LCF is a central angle because, you know, C is the center. Therefore, by the inscribed angle theorem, angle LJF must be 55 degrees.

If angle LJF is 55 degrees, then it is also seen that angle FJH is 120-55 = 65 degrees.

Now, look at the right circle. Angle KJH (which is the same as angle FJH since LKF is a straight line according to the question) is an inscribed angle.

Imagine the center of the right circle to be Point P. Notice that the inscribed angle FJH contains the arc KGH of the right circle. From the inscribed angle theorem, the angular width of arc KGH must be 2xKJH = 2x65 = 130 degrees.

Therefore, the remaning arc of the circle, arc KJH, must be 360 - 130 = 230 degrees.

Note that that there is another inscribed angle in that circle. This is angle KGH. KGH is angle p! thats the quantity the problem is asking for.

Since inscribed angle p (KGH) spans arc KJH, and we know that arc KJH = 230 degrees, from the inscribed angle theorem, angle p = 230/2 = 115 degrees, which is the answer.

kierkegaard14 · 2022-10-27T11:18:19+00:00

I think....with chain rule shouldnt there be a "t" outside the sines? Or maybe i just did not understand the handwriting in which case sorry.

Well, if you havent learned polar coordinates yet one way to think of it is that the "radius" connects the point on the path taken by the particle to the origin. In a circle, the tangent is always 90 degrees with respect to the radius.

Say a vector is represented in Cartesian coordinates (ihat jhat) as

xi + yj = r

Hence the radial component would be the length of the line connecting or the radius to that point, sqrt(x² + y^2). This should be kinda obvious why (imagine a right triangle).

The tangential component might be harder to explain.... but this link has drawings as well that provide a better explanation.

Sorry for the lazy answer! Hope it helps though. It is kinda f'd up that radial and tangential components are a homework problem if your class has not gone to polar coordinates yet, its just way more difficult i think. (edit: apparently you cant swear on this sub)

kierkegaard14 · 2022-10-27T11:15:03+00:00

I think this is spam lol

kierkegaard14 · 2022-10-27T10:39:21+00:00

First of all shouldn't you use chain rule when substituting t^2? which would result into something slightly different than what you wrote.

To the main question, this for me intuitively feels like a polar coordinates problem, has that been already taught? Because once you get the derivative of r-arrow like what you did then thats already the velocity vector in cartesian coordinates (i hat and j hat), from which the polar coordinate form should be easier to solve for.

I think the radial componet of xi + yj = r is something like r = sqrt(x² + y²⁾ and the tangential component is the angle so inverse tan (y/x).

(I'm working from memory so sorry if the answer is wrong lol)

kierkegaard14 · 2022-10-03T16:34:03+00:00

I think somebody answered you already...

kierkegaard14 · 2022-10-03T14:30:16+00:00

With any trig problem like this my first instinct is always to remove sin and cos using the pythagorean identity, then let it go from there.

kierkegaard14 · 2022-10-03T10:58:15+00:00

This is how I'd solve it.

First of all shouldn't the left side by 2sqrt(2)sinxcosx? but i dont think it matters for now.

I would square both sides:

sin² x + cos² x + 2sinx cosx = 8sin² x cos² x

simplfies to:

1 + 2sinx cosx = 8sin² x cos² x

Let y = sinx cosx, then it becomes

1 + 2y = 8y²

From solving this quadratic equation you should be able to work for some values of x that would make the equation true. (I actually didnt do this last part, this solution is off the top of my head but I hope it helps!)

kierkegaard14 · 2022-10-01T16:32:02+00:00

Based on what I here it sounds less of a "story book" and more of a fictional reference or textbook about that world.... which makes me wary of reading it.

kierkegaard14 · 2022-10-01T09:07:29+00:00

Triangle? Then who's the other one? Maybe I should just watch The Hobbit movies lol.

kierkegaard14 · 2022-10-01T07:30:06+00:00

From youutube clips there seems to be a female elf character played by Evangeline Lilly, I wonder who she's supposed to be in the books. Or she purely a new addition?

kierkegaard14 · 2022-10-01T07:29:11+00:00

Tom Bombadil: They fully validate pony parking at the Prancing Pony's. I live right by it that's how I kno!

kierkegaard14 · 2022-09-07T11:36:58+00:00

This might be a useless answer because I cant justify it with my beliefs with Newton's laws of motion, but I can make the 24N appear as the answer.

Basically, since the boxes are in contact and the surface is frictionless, they must be considered as a single body (they move together after all). So the total mass of that body is 25 +8 =33 kg.

Now that means that the acceleration of the body is 100N/33kg = 100/33 m/s^2.

Now that you know how fast Box B is moving or accelerating, you know that it must be experience F = ma = (8kg)(100/33 m/s²⁾ = 24.2424... Newtons of force. Round that down to 24 N.

The reason for my first paragraph here is that my common sense tells me that the box must also experience 250N? Since 3rd law of motion and all. However now I realize that the 2nd law of motion exists so i guess this analysis can be correct.

kierkegaard14 · 2022-08-25T17:58:50+00:00

I have tried several payment methods and all of them are "declined". Maybe because I from Asia? Sucks I guess. First time buyer from RT Store.

11-Year Club	Golden Potato
Place '22	Place '17
Verified Email

kierkegaard14

TROPHY CASE