What is Difficulty: Definition and 268 Discussions

Degree of difficulty (DD, sometimes called tariff or grade) is a concept used in several sports and other competitions to indicate the technical difficulty of a skill, performance, or course, often as a factor in scoring. Sports which incorporate a degree of difficulty in scoring include bouldering, cross-country skiing, diving, equestrianism, figure skating, freestyle skiing, gymnastics, rhythmic gymnastics, surfing, synchronized swimming and trampoline. Degree of difficulty is typically intended to be an objective measure, in sports whose scoring may also rely on subjective judgments of performance.

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  1. jamalkoiyess

    Schools Difficulty of getting into top colleges

    Hello PF, Can anyone tell me how hard it is for anyone to join MIT or Harvard for exemple in engineering or physics for graduate studies?
  2. Kilo Vectors

    Wanting to study electronics, difficulty? preparation?

    Hello I am currently a university student studying business. I am going to apply to a program in electronics and information engineering. I liked the program because it is a mix of computer science (algorithms, operating systems, software engineering and computer architecture modules) , IT...
  3. K

    Mathematica Difficulty in solving an integral in Mathematica

    Hello, I have to solve the following integral in Mathematica but although I don't get any mistakes the value I get is <10^-700 which can't be right! For the following values b=0.052868 c=0.998047 g=0.00762712 s=0.902416 I have to solve the following: Fx =...
  4. N

    Difficulty understanding vector transformation law

    I am having a hard time understanding vector transformations. I know that vectors must transform a certain way and that dual vectors (or covectors) transform the "opposite" way. What is strange to me is that the basis vectors transform like dual vectors and the basis dual vectors transform like...
  5. M

    Quantum QFT books in order of difficulty

    Hi, I'd like to ask you if you could write a list of QFT books in order of increasing difficulty. Thanks!
  6. F

    Difficulty of question asked in PGRE exam

    Hi friends , I am an electrical engineering student , interested in applying M.S in physics program in Europe . So i have started preparing for this , when i searched the web how to study for PGRE , most effective and common suggestion is go through the recommended books for each subject and...
  7. Y

    Difficulty understanding ∫ P(X).X^2 dx = <X^2> ?

    I know for discrete random variables Σ P(x).x = <x> Translating for continuous random variables I'm also aware of the result ∫ P(x).x dx In my lecture notes ( I more or less transcribed from what the lecturer said ): ∫ P(x).x^2 dx = <x^2> , should it not be ∫ P(x^2).x^2 dx = <x^2>? Does...
  8. J

    Difficulty computing second derivative value in SHM problem

    Homework Statement The displacement of a machine is given by the simple harmonic motion as x(t) = 5cos(30t)+4sin(30t). Find the amplitude of motion, and the amplitude of the velocity. Homework Equations x''(t) = -4500cos(30t)-3600sin(30t) The Attempt at a Solution [/B] I should note that...
  9. S

    Difficulty of the Physics Series courses for Science/Enginee

    Well known it is that the fundamental mechanics and the fundamental E&M courses of Physics for the science and engineering students are very difficult. Then the next course of this series, "Modern Physics", may seem so much less stressful, and at least a bit or more easier. Is this common? Is...
  10. E

    What Are Common Mistakes When Calculating the Laplacian of |r|?

    Homework Statement Given: |r|=√(x^2+y^2+z^2) r=xi+yj+zk (i)Find the partial derivative with respect to x of |r|. (ii) Find the Laplacian of |r|. Homework EquationsThe Attempt at a Solution For (i) I got x/|r| but then for (ii) I got 2/r which I don't think is correct
  11. L

    Having difficulty working out a Char. Pol. for Eigenvalues

    Given the following matrix: 2 3 0 3 2 4 0 4 2 I'm having a difficult time working out the characteristic polynomial. I used the shortcut that I saw on YT, where it is (I am using x instead of lambda) X^3 - (trace) X^2 + (A11+A22+A33) X - DET(A) I got the following: trace is just 2+2+2 = 6...
  12. P

    Finding constant acceleration, unit difficulty

    Homework Statement An Indy 500 race car's velocity increases from 4m/s to 36m/s over a 4 second time interval. What is its acceleration? 4m/s is the initial velocity, 36 m/s is the final velocity, and time is 4 seconds. Homework Equations final velocity = initial velocity + (acceleration x...
  13. S

    Difficulty of undergraduate homework problems

    I am an advanced undergraduate student, and I still remember the days when I could open my mathematics textbooks, read through a few sample problems, and then blaze my way through the exercises with little or no help. Come university, and my freshman year, and things changed dramatically. I...
  14. M

    I am having difficulty with a Gamma Distribution problem

    Homework Statement Automobile accidents occur in the United States over a 72 hour holiday period like events in a Poisson process with parameter lambda=10/hr. V is the time until the 10th accident a) what is expected value of V or E[V] and standard deviation? b) What is the probability that V...
  15. A

    Difficulty checking the solution of differential equation

    Homework Statement The differential equation is xy'-2y= x3ex Check the solution y=x2 ex Homework Equations Just plug in The Attempt at a Solution y' = x2ex + 2xex Having problem solving for x.
  16. D

    Difficulty solving the following quadratic equation

    < Mentor Note -- thread moved to HH from the technical math forums, so no HH Template is shown > Hi, I'm having difficulty solving the following quadratic equation x^2-(660/x-5)-91=0. The fact that the middle term has an x-5 rather than just an x that is throwing me Can anyone please help...
  17. PWiz

    Testing Horrendous SAT difficulty level in English?

    Hello all. I plan on appearing for the SAT / ACT soon (I'm still sort of on the fence between the two), and I've heard that the SAT English difficulty level is absolutely brutal. This is tipping the scales in favor of ACT, but then I've also heard that scoring in ACT writing can prove to be very...
  18. M

    Having difficulty with concept of turning points

    Homework Statement I understand how to solve for stationary points, and then take the second derivative and input the values of x to determine the nature of the stationary points, if x > 0 then the stationary point is a minimum and if x < 0 then the stationary point is a maximum. What I am...
  19. T

    Engineering Electrical vs Electronic engineering difficulty

    Hi guys, I have completed my first year engineering courses and about to start my second year. I enrolled for computer engineering but have decided to change to either electrical or electronic engineering. So my main question is which is more harder between the two ? I know the main differences...
  20. C

    First year physics difficulty level

    I'm starting a physics major this year and I'm currently enrolled in foundation physics (algebra, vector based). However, during second semester I'll be doing doing a regular physics unit which is based around technology. The main topics are Electromagnetism (LOTS and LOTS of circuits work...
  21. DivergentSpectrum

    Conceptual difficulty with faradays law

    As i understand, the induced current in a wire equals -d(∫∫B⋅dS)/dt What is S? I know it has to be an open surface for the flux integral to be non-zero, but over what surface do i do the integral?
  22. B

    Comparative Difficulty of Sciences?

    Before I get blasted by anyone, I just wanted to say that I'm asking this as a matter of curiosity and am in no way suggesting that some people/academic subjects are "better" or "worse" than others. It's strictly an intellectual question for me with no personal meaning or any other type of...
  23. P

    Difficulty in understanding the notation

    We have this stationary metric, $$ds^2 = e^{2U}(dt+\omega_idx^i)^2 -e^{-2U}dx^2$$ The book wrote down the spin connections of this: $$ \omega^{0i}=\partial_ie^{U}e^0 +e^{3U}\partial_{[_i\omega _k]}e^k $$ and $$ \omega^{ij}= e^{3U}(\partial_{[_i\omega _j]}e^0-\partial_{[_ie^{-2U}\delta_j]k} )$$...
  24. A

    I have difficulty understanding quantum physics

    Like I was reading Stephen Hawking and while I found quantum physics interesting, I had trouble truly understand it. I mean I know it's the study of very small particles and stuff like you cannot predict where an electron is if the more you know its velocity but I had trouble understand the why...
  25. C

    Difficulty following example in Taylor's Classical Mechanics

    http://i.imgur.com/GP6QorG.jpg I don't follow the integration in it. I'm assuming Fx(x,0) and Fy(1,y) are the partial derivatives of F with respect to x and y, respectively, but given that, I can't seem to get my head around the result where the partial with respect to x is Fx = (x, 0) instead...
  26. M

    Difficulty working with SI and derived SI conversions

    The physics textbook I'm working with doesn't seem to give me the required background for working with and understanding SI and derived units. Here is an example of something i am struggling with: In studying fluid resistance, the book starts by displaying 2 equations. 1 is for fluid...
  27. throneoo

    Difficulty with evaluating an integral

    Homework Statement How to evaluate the anti-derivative of [x+(7x^2)]^(1/3) ? 2. The attempt at a solution I've attempted to do so via standard integration techniques , i.e. substitution and integration by parts , but the problem simply becomes increasingly complicated . I've even tried...
  28. Solibelus

    Difficulty understanding EMF due to a changing magnetic flux

    Hello everybody, I'm studying classical electrodynamics and I'm having a difficulty grasping the concept of EMF. I'll try to explain what causes my confusion. Say I've got a conducting loop, an electrical wire, with some resistance R which contracts (or expands) with time. Let's put that loop...
  29. G

    Still having difficulty in my introduction to fields

    Homework Statement I was reading in a book that, " For any function f(x) whose functional form changes from f(x) to f'(x), we can write \bar{\delta}f(x) = f'(x) - f(x) = {f'(x') - f(x)} - {f'(x') - f'(x)} =...
  30. C

    Difficulty understanding "donor" and "acceptor" energy levels.

    Hi all, I think I understand the concept of doping a group IV semiconductor material with a group V atom which has one extra valence electron to "donate" to the conduction band, or doping with a group III atom with one too few electrons which will "accept" an electron from the lattice and...
  31. S

    MHB How Can I Correctly Derive the Quadratic Equation from a Train Speed Problem?

    I'm having difficulty deriving a quadratic from the info in this question: A train usually covers a journey of 240 km at a steady speed of \(v \text{ kmh}^{-1}\). One day, due to adverse weather conditions, it reduces its speed by 40 \text{kmh}^{-1}\) and the journey takes an hour longer...
  32. interhacker

    Difficulty Imagining things a possible setback?

    I'm a high-school graduate, on my way to college this September. I have this problem. I like mathematics and physics a lot, and, at least up to high-school level I've been getting good grades in it (I won the Cambridge Outstanding Learner's Award for topping A-Level Physics in my region). In...
  33. T

    Difficulty level of upper div physics classes?

    I'm not sure if this is off-topic for this section of the forum but I wasn't sure where else to post it. I'm substantially behind compared to other physics majors at the moment (3rd year student with enough credits to be considered mid 4th year student) so i wanted to pick up the pace. I like...
  34. aboojoo

    Difficulty understanding formula and area under v-t graph

    1. The problem For sake of format I attached the a screenshot of the course material I'm having difficulty wrapping my walnut around. Which is how: Total Displacement = Area of Triangle + Area of Rectangle or Δvector d = Atriangle + ARectangle or Δvector d = 1/2 (V2-V1)Δt +V1*Δt...
  35. M

    Difficulty in electroetching of 1050 aluminum alloy

    Dear friends I have tried to electroetch 1050 aluminum alloy by 5ml phosphoric acid + 95ml H2o under 1 to 10 volts. However, it was a complete failure even after etching for 6 min. Please help me if you know how to overcome this problem. Thank you very much Best regards
  36. E

    Why Is Calculating Slit Spacing in a Diffraction Grating Confusing?

    Okay, I understand this is a highly trivial problem, yet for some reason, it is bestowing much difficulty upon me. If a diffraction grating has 500 slits/mm, what is the spacing between each slit? Evidently the spacing between each slit is given by the inverse of that ratio. I am having...
  37. B

    Difficulty manipulating a limit question (secant method)

    Hey, I'm really struggling with this 'show that' question regarding the secant method, I just keep going in circles and I think I may be heading in completely in the wrong direction because I'm not getting anywhere. Homework Statement We're given that, if x* is the zero of f then (we...
  38. D

    A problem that puts me in difficulty

    Homework Statement Let a,b,c,d be real number that satisfy the property that a + b = c + d and a^2 + b^2 = c^2 + d^2 . Show that a^n + b^n = c^n + d^n for any n , a natural number ( with n > 0 ) . Homework Equations x^n - y^n = (x-y)(x^{n-1} + x^{n-2}y + x^{n-3}y^2 + ... +...
  39. G

    MHB Having difficulty in solving the equation

    if a,b,c are in continued proportion .prove that (a+b+c)^2/(a^2 + b^2 +c^2 )=(a+b+c)/(a-b+c)
  40. applestrudle

    Difficulty picturing skew lines

    Is there only one point where the line connecting the two skew lines is perpendicular to them both? And is that point always always always the place of closest approach? Thank You
  41. T

    Modeling T-Stub as Beam (having difficulty)

    Hi all, I am trying to find the slope of a T-stub joint at the bolt in order to find the bending stress of the bolt. I have drawn 1/2 of the T-stub as a beam. The beam analysis requires (for physicality) that the slope at each side of the beam to be zero. There is an applied load, a bolt...
  42. K

    Difficulty creating a response surface

    Hi all I am struggling to create a response surface for some data I collected. I have been asked to create a response surface to get a better understanding of how the two inputs of interests affect the output. I threw together a multiple linear regreession model since it was simple but my...
  43. J

    Difficulty with summation of non-central chi-squared random variables

    Hi, I am struggling trying to find the (equation of the) pdf of the sum of (what I believe to be) two non-central chi-squared random variables. The formula given on wikipedia (http://en.wikipedia.org/wiki/Noncentral_chi-squared_distribution) shows that the random variable associated with...
  44. H

    Difficulty of getting a job as a community college math professor?

    Hello, I've come to the point where I realize: I'm supposed to teach. I've tutored for years, taught small groups, etc. Also, I want the summer to pursue my other interests. I don't want to do research or anything; just teach. I was just curious as to how competitive these jobs are...
  45. M

    Difficulty finding these two limits

    Homework Statement Given that lim f(x) = 4 x → 2 lim g(x) = -2 x → 2 lim h(x) = 0 x → 2 find the limits that exist for the problems below. If the limits do not exist, explain why.c) lim √f(x) x → 2 e) lim (g(x)/h(x)) x → 2 Homework Equations lim √f(x) x → a = √(lim f(x)) x → a and...
  46. M

    Having difficulty understanding radicals

    I know how the very basics but then I get given a question like this. ##\sqrt{9-3x}## and I think I can divide both by 3. ##3\sqrt{3-x}## and so ##x=3## Then I get ##\sqrt{4x+12}## and again I can take 4 from each ##4\sqrt{x+3}## and so ##x=-3## Is this the correct way to be solving these...
  47. A

    Troubleshooting Seldon Package Compiling Error in Visual Studio 2010

    I'm having some difficulty compiling a test project within Visual Studio 2010. I'm trying to test the Seldon package, but keep getting errors during build. Specific errors I'm getting include (and vary between): // Headers from CLAPACK, downloaded at http://www.netlib.org/clapack/. //...
  48. R136a1

    Difficulty checking group axioms

    Let ##G## be a set equipped with a binary associative operation ##\cdot##. In both of the following situations, we have a group: 1) ##G## is not empty, and for all ##a,b\in G##, there exists an ##x,y\in G## such that ##bx=a## and ##yb=a##. 2) There exists a special element ##e\in G##...
  49. A

    Struggling with Math: Any Book Recommendations?

    Hi, I've studied mathematics at high school and I will start university next year. I'm worried about my mathematical knowledge in general. There are many "gaps" which lead to confusion. To give you some examples: 1) I've difficulty understanding why, for instance, 5 - (-2) = 5 + 2. The only...
  50. D

    Stochastic Process prerequsites and difficulty?

    My university is offering a course called "Stochastic Process". The only prerequisites to this course according to my university is a course in Probability which uses the book by Rosen. I've read elsewhere that the course actually requires more of analysis (functional analysis and measure...
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