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Robert Cruikshank
United States
Приєднався 14 жов 2011
Symmetric Difference of Sets is Associative
A short proof, illustrated with Venn diagrams, and using a symmetry argument.
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Відео
How Beta is Conjugate to Binomial
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A derivation of the relationship between prior beta distribution, binomial data, and an updated beta distribution.
The Beta Function: Solving the Defining Integral for integer a,b
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The Beta Function (as opposed to the Beta Distribution) is defined both by an integral and as a combination of gamma functions. I show the two are the same for the case of integer inputs. Wikipedia has more general proofs but I thought this case has more straightforward calculus.
CDFs for Exponential Rayleigh Weibull and Pareto Distributions
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(revised) I show a pattern in the formulas for a few different probability distributions. These formulas are often scattered in a textbook so I brought them together.
Low Pass, High Pass, or Bandpass Filter?
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Almost zero math. Mnemonic and explanation for several simple cases of filter networks. This is for grasping the concept.
Counting Radial and Angular Nodes in Atomic Orbitals
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A Two Minute Video with the rules and four worked examples.
From Complex Roots to Real Solutions
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Here's a detail that often gets covered quickly in differential equations class. Apologies for the blurriness, I seem to be cursed when it comes to camera technology.
Electric power: Definitions (A Two Minute Video)
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Definitions of power, current and voltage, with brief examples. Made for a viewer by request!
What is E[E[X|Y]] ?
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I work a tiny example with numbers and give a symbolic proof at the end. Hopefully this reduces confusion!
Adding Vectors: TLDW Version
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Here's the 2.5 minute version of the 16.5 minute video I just posted: ua-cam.com/video/bKfto0MKFrg/v-deo.html Season to taste! #physicstutor #physics #tutoringservices #vectors
Adding Vectors: Every. Single. Step.
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This video is long; it assumes very little knowledge, and is meant for students facing most of the ideas for the first time. I have created a TL;DW version that zips through the same thing at 5x speed. ua-cam.com/video/5Y79FUVpgUU/v-deo.html I hope this helps to save students struggling with the beginning of #physics class! #physicstutor #vectors #tutoringservices
A Tricky F = ma Problem from Kleppner and Kolenkow 1st ed
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I solve problem 2.19 from K and K in the first 2:30, then problem 2.20 in the rest of the video. linktr.ee/knowledgeoncall robertthetutor.online
Holder Inequality Lemma: A 2 minute proof
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The Cauchy -Schwarz Inequality is widely used; it turns out to be a special case of the Holder Inequality. That in turn depends on this little lemma, which can be proven with a bit of calculus. The proof is mostly taken from Casella and Berger.
Power and Intensity (an example with sound energy)
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I work an example of a speaker emitting sound, and talk about the energy, power, intensity, and sound intensity level (dB). This is another video made with slides and a VoiceOver. These certainly upload faster! I'm still getting the hang of making a voice over, so I didn't fight to trim this one down to two minutes flat.
How Voting Works
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Just spelling out things that everybody should already know. Elections are much, much easier than civil war.
Why does the Fourier Trick Work? Using trig not integration by parts
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Why does the Fourier Trick Work? Using trig not integration by parts
Moment and Shear All Along a Cantilever
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Moment and Shear All Along a Cantilever
From Physics 1 to Engineering Statics: Cantilever Example
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From Physics 1 to Engineering Statics: Cantilever Example
Nodes and Antinodes in an Open Pipe
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Nodes and Antinodes in an Open Pipe
100 cm^2 is NOT 1m^2! Visual Examples in Metric
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100 cm^2 is NOT 1m^2! Visual Examples in Metric
Hydrogen and Energy (clearing up confusion)
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Hydrogen and Energy (clearing up confusion)
How to Clean a Quadra-Fire 1200-I Pellet Insert (Stove that fits inside a fireplace)
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How to Clean a Quadra-Fire 1200-I Pellet Insert (Stove that fits inside a fireplace)
Deciphering the Definition of Complete Statistic
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Deciphering the Definition of Complete Statistic
The Definition of Sufficient Statistic Looks Weird (a 2 minute remake)
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The Definition of Sufficient Statistic Looks Weird (a 2 minute remake)
Nitrogen has MW of 14 and not 28 as you mentioned but calcs are still based on 14.
Hold on: I understand you wish to say that little the PDF of Y is the derivative of the CDF of Y (i.e., the statements in the top-right corner of the whiteboard. However, you wrote that F_X(sqrt[y]) i.e., the cumulative distribution function of random variable X as a function of observed value sqrt(y) is 1/(2sqrt(y). You subsequently substituted this expression for F_Y(y) (i.e., the cumulative distribution function of random variable Y as a function of observed value y). is this appropriate? It seems like some amount of explanation would be needed, though? I.e., it seems that you simply used F_X(sqrt(y)) interchangeably with F_Y(y)
EDIT: Ah, nevermind, I see/am reminded now that earlier, we have a statement equating F_Y(y) to be equal to F_X(sqrt(y)). My attention was darting back and forth a little bit too much between different resources on the computer screen and my own sheets of paper haha. This has been a good struggle; I hope this will help me remember things for my subsequent tests and evaluations :)
I wonder: Is it sufficient to simply without justification that P(X^2 < y) is precisely equivalent to P (X < sqrt(y))? I know it's obvious that X is SQRT(X^2) and that sqrt y is SQRT(y), but is it also fully defensible to say that P(m<n) is always equal to p(sqrt(m)<sqrt(n))?
That's why I specified a positive domain. In general, if X^2 < Y, then -SQRT(Y) < X < SQRT(Y)
Provided that Tis symmetric, show that tr ( nabla* T)=0 I am really got confused on this topic
I can see why! I went hunting for definitions. nabla*T seems to be either rank 1 or rank 3 tensor, and in either case I don't know how "trace" makes sense. Trace is a contraction of a rank 2 tensor. When in doubt, study the definitions! You may have gotten a def in lecture or something. Figure out what nabla*T IS in the first place, and what the def of trace for it is. Good luck!
❤ amazing short and sweet
The reason why they have to switch it up in general is that the expression P(theta | U, data) = P(theta| U) does not make sense unless you're a Bayesian. If you're doing frequentist statistics, the parameter is not random, just unknown. This means that the expression P(theta) simply does not make sense. This also goes to show how many people are intuitively Bayesian to begin with hahaha.
Yes, I have heard this argument. As far as I can understand (which is limited), it leaves math behind and dives into philosophy. Granted, the philosophy of probability theory is seriously messed up to begin with. It wasn't until I tackled advanced statistics that I realized that I owed QM an apology for calling it nonsensical--it merely inherited most of its problems from probability theory. But to get back on point: if I fully understood the issue you are describing, I would have made another video about it. Sadly I must leave that to better minds than my own.
Thank you sir Tomorrow I am going to write a paper in Tesla in power systems
perfect, helped me understand this simple concept more effectively
Wow incredibly efficient video, thank you for helping me grasp this topic
Thank you I finally understood this 🙏
wow , thank you very much, it helps a lot
Thank you sir very very much for the information and by the way I had a doubt That why is biot savants law only restricted to steady state current flow?
It turns out that electric and magnetic field changes are limited by the speed of light. So it gets really complicated really quickly if you have to take into account exactly when and where the particle was moving how fast, the time lag makes it a mess to calculate. Steady state problems skip all that.
As of August 2024, a new fare payment system has been implemented on subways, buses and trolleys. In addition to paying with your charlie card, you can also tap your credit card, or a phone with a digital wallet on the new screens by the fare gate/box. Just make sure to tap your phone/credit card on the screen and your charlie card on the circle. Enjoy the T.
Clearest most understandable video I have watched in my life
Great video!
Very well made!
Thank you. Very easy to understand. Brilliantly explained. Respect from Pakistan.
absolutely great video
at 0:31 you say "pressure times volume has the units of work", but the whiteboard says "pressure times the change in volume has the units of work"
Both are true. Volume and change in volume have the same units.
Thanks!!
This video was incredibly helpful! Thank you for posting this.
I can't explain how much it useful for my exams. I was always confused in batteries one. You cleared all my doubts. Thanks a lot from India🇮🇳🇮🇳
Thanks! Also for the current we can choose any direction all the time?
Yes! It's just like choosing a coordinate system, there's no wrong answer. If you get a negative number for your current that means it is actually flowing the other way, just like if you say up is positive and get a negative vertical velocity it means the object is going down. Just be consistent.
Wow, this man can explain quantum physics to a toddler! BTW, how did I get here? Oh yeah, I was trying to learn what the f natural gradient is!!!!
Well, maybe not a toddler, but I did channel Dr. Seuss for it at one point: www.quora.com/search?q=Dr%20Seuss%20quantum
You just showed that a commutative binary function is associative iff it satisfies a stronger form of commutativity. It's the first time I see that idea!
Thanks for clearing my doubt
The field lines of a quadrupole: ua-cam.com/video/1I_CGFyK5cg/v-deo.htmlsi=gUBuYevLHnP9t3JJ&t=371
Indiaa❤
Thanks.
My teacher taught me complex circuit without making my basics clear so i cant understand that but you made my basics crystal clear
Thanku❤
I found your channel googling tesla unit of measurement. Thank you for teaching me this sir.
This helped me out immensely. Thank you!
I would give this 1000 likes if I could. Thank you!
Clear and informative. Thanks
I'm studying to be an actuary, a big thanks to you for making these!
Fantastic Explanation! 😊
Thnxx
Thank you so much.
Bro your a life saver❤
What a wonderfully hel pful diagram - thank you!
Thanks so much!!
I saw this video before 3 month it was help full. But I forgot it. Now this time I searched on UA-cam,but you tube don't suggest me so I searched it on Google and found it. Tank you sir
Why not leave the small x's and y's as they are (not take their logarithms), and try to figure out a good enough equation to describe the relation between them using some other way? (I know the result won't be a straight line and won't be a first degree equation).
Because how do you measure a "good enough" equation? The formulas we use essentially say, rewrite the variables until we have a linear relationship, then fit the data to the line, and then if need be transform back. You can skip that if you can come up with a better way of defining "good enough" that is quantitative.
@@robertcruikshank4501 thanks for the reply
I wonder why it took so long for me to find this channel ❤️ Keep it up Mr. Cruikshank!
you are an absolute legend... appreciate your work!!
This is amazing. So simple and straight to the point. Thank you.
Thx, Doc. We in the streets turning up to this one. Using exponential families right now for most sufficient statistic work, but I am hoping to get this theorem down well. Also, you looking sharp, homie. I like the haircut and fit. Fresh.
Stuck on how you got 6.62V @1500resistor. I do .0441*1500 and come up with 66.15. Am I missing something? Thanks.
Good catch! I missed a zero, since .012/e = .00441, not .0441. Since I had it correct on my calculator, my next calculation came out right so I didn't spot my miscopy.
wise person