# 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. ### B Estimate the difficulty of a mountain route

Hello guys, I am not into this field and finished my college long ago. I am trying to find a formula to estimate the difficulty of a mountain route. The input is: D = linear distance between start and destination (as given by Google Maps) in m, km, whatever. Both points are considered at the...
2. ### Engineering Difficulty in Understanding Inverter Terms

I have a great difficulty in understanding the current and voltage ratings of the inverter, at the input of the inverter the ratings are different compared to the output side. What are the formulae of those conversions example, If i check the above diagram, power supply is 24V, 1.6APk a. Does...
3. ### Difficulty visualizing given set

Okay so I know, that if the radius is 0, the z coordinate will run from -1 to +1. If the radius tends to one, the z coordinate will tend to 0. But I still cannot imagine how this set looks like, help would be appreciated. Thank you.
4. ### B A difficulty with the equivalence of all inertial reference frames

Although I am not a physicist, I am interested in physics, and recently I've been reading about special relativity. I have a doubt about it, a difficulty I see in the equivalence of all inertial reference frames which I haven't found solved anywhere, and I've thought perhaps you in this Forum...
5. ### I Difficulty in understanding step in Deriving WKB approximation

In Zettili book, it is given that ## \nabla^2 \psi \left( \vec{r} \right) + \dfrac{1}{\hbar ^2} p^2 \left( \vec{r} \right) \psi ( \vec{r} ) =0 ## where ## \hbar## is very small and ##p## is classical momentum. Now they assumed the ansatz that ## \psi ( \vec{r} ) = A ( \vec{r} ) e^{i S( \vec{r} )...

7. ### Difficulty with machining bismuth, any suggestions/tips/other ideas?

Hello all, we are working with some bismuth for a series of upcoming experiments and are trying to initially keep the purity high for better neutron activation measurements. Unfortunately there has been some difficulty with machining steps on the final pieces with chipping due to the material...
8. ### B Difficulty with understanding whether 1/n converges or diverges

Hi, I have a quick question about whether or not the infinite series of 1/n converges or diverges. My textbook tells me that it diverges, but my textbook also says that by the nth term test if we take the limit from n to infinity of a series, if the limit value is not equal to zero the series...
9. ### Other Are there guides for assigning problem difficulty levels in ME textbooks?

I was recently looking at some freshman ME textbooks that had over 100 problems per chapter. Are there resources that identify the difficulty level for each individual problem (for example: easy, medium, hard, fiendish) for the common textbooks? I am not looking for solution manuals. Another...
10. ### Classical Rate the Quality & Difficulty of the Book

HI! Can you rate the book i mentioned below in terms of quality of concepts and the problems given. What do you think about the difficulty of the book?(For a moderately beginner person). Thanks! The link is .. [Moderator's note: link removed].
11. ### Difficulty with "Exists" & "Let" or "Arbitrary"

1. when writing a proof, I stumbled upon cases where I wondered if the following two are equivalent?: a. " There exists ## n \in N ## such that ___ " b. " Let ## n \in N ## be arbitrary such that ___" Are these statements the same? Is ## n ## in both of them the same? 2. Suppose I have the...
12. ### Difficulty with Lagrange multipliers in Kardar's Statistical Physics book

Alright, so I did some progress and then I got stuck. After some time I went to check the solution. Up to some point, it's all well and good: I understand everything that is happening up to the point where he takes the partial derivative of S wrt ρ(Γ). I don't understand how he gets the...
13. ### The difficulty of learning Electromagnetism vs Classical Mechanics

There was an old thread comparing the difficulty of classical mechanics and electromagnetism. The consensus was that electromagnetism is more difficult, and substantially so according to some. The thread was no longer open for replies, but it got me suspecting that we're comparing apples to...
14. ### Difficulty of Project Euler problems 1-100; now versus then

Hi I recently noticed that the first Project Euler problem was published in 2001! The first 100 problems were all published before 2006. That made me curious; What I wonder is how different the difficulty is now versus then... I mean, I can think of two factors that make things easier: 1. The...
15. ### Having difficulty increasing my load power factor above 0.95

I have an inductive load (120 volts AC at 0.5 amps AC at 60 Hz, 0.9 power factor before correction) that is a connected to the grid. I have been trying to increase the power factor above 0.95, but no matter how much I tune the power factor correction capacitors I cannot increase the power factor...
16. E

### B Difficulty with derivatives using the Lorentz transformations

Two frames measure the position of a particle as a function of time: S in terms of x and t and S', moving at constant speed v, in terms of x' and t'. The acceleration as measured in frame S is $$\frac{d^{2}x}{dt^{2}}$$ and that measured in frame S' is $$\frac{d^{2}x'}{dt'^{2}}$$My question...
17. ### MHB Challenge. Difficulty level - medium

In a regular quadrangular pyramid the area of a side surface is twice as much as the area of the base. Find the ratio of the height to the length of the side of the base of the pyramid.
18. ### Difficulty with this Problem involving a Pully and Cart

My attempt is also attached. Basically, I think I have (a) down. The only issue is I am getting the wrong answer, and I was hoping one of you could let me know if the answer key is wrong or the way I did it was wrong? The answer is 1.823m/s^2. Also, for the second part, I am really not sure...
19. ### General Physics I Question: Moment of Inertia Problem Difficulty

Hi everyone, I am honestly pretty confused as to where to start with this. Can anyone give any pointers as to where I could possibly go, for (a) and (b)? Thanks!
20. ### Difficulty understanding Centre of Gravity

Hey, This isn't a homework question I need help with but more of a concept I can't seem to grasp. I understand that Centre of Gravity is: the point on a body where all the weight can be considered to act. And I understand how to find this point on different types of bodies. However, this...
21. ### I'm having difficulty expressing a binomial expansion as a sum

I found the first 4 terms of the series: ½-(1/16)x^2+(1/64)x^4-(7/1536)x^6. I cannot however simplify this to a sum. the 7 in the numerator of the last term of the above expansion is the sticking point.
22. ### Taking 4 difficult ENGR related classes and working a part-time job?

I am taking next semester Differential equations, University physics 2, Electrical circuits class and lab and an Introduction to engineering course at a community college and I am planning to work part time. Is it a good idea or at least doable to do those classes and take a part-time job less...
23. ### Physics Ranking Difficulty

What is the easiest topic from optics,mechanics,thermodynamics and electricity(DC)?Can someone rank them from easiest to hardest? I want to know that because I'm taking my IB and I don't know which one to pick.I found something about this ranking but I'm not sure if this is the correct one...
24. ### MHB Having difficulty finding the elements in each set

Find the elements in each set given that: U={1,2,3,4,5,6,7} A={1,3,5,7} B={2,4,6} C={1,2,5,6} D={2,3,4} A) C intersect D B) C-D C) (A union B) union C D) (C union A)' -D
25. ### Difficulty with a Point Charge Particle in Electrodynamics

Point Particle in Relativity and Electrodynamics: “The Classical Theory of Fields” – by Landau and Lifshitz, in its discussion about classical size of a particle, concludes that:- Thus we come to the conclusion that in classical (non-quantum) ‘relativistic mechanics’, we cannot ascribe finite...
26. B

### Classical Difficulty of Morin's problem

What book do you think is better for a 1st year college Physics student: "Introduction to Classical Mechanics (with problems and solutions)" or "Problems and solutions in Introductory Mechanics" of D. Morin? Despite the fact that the titles are very similar the two books are different, but I...
27. ### Courses Grad vs undergrad difficulty and workload

I'm going to be taking graduate physics courses this semester and I need to decide how many to take. My question is how does the difficulty and work load of graduate physics courses generally compare to upper level undergraduate physics courses. I know there is variation between courses and...
28. C

### Difficulty with Mathematical Methods of Classical Mechanics

Homework Statement A friend and I are going through Vladimir Arnold's Mathematical Methods of Classical Mechanics, but I think my lack of a background in pure math / proofs is seriously hampering my ability to do any of the problems in the first chapter. For example: PROBLEM. Show that if a...
29. ### Difficulty extracting fluid from balloon via syringe

Hello, New to the forum, so apologies if this is not the correct sub-category. I am testing compliances of materials by filling balloons with different fluids. I do this by filling up a 30 mL syringe with fluid and placing it into an infusion pump set to infuse at a rate of 0.1 mL/min. The...
30. ### Why Do I Need So Many Resistors? Is It Possible to Reduce?

Hello. I wonder if I can take some of these resistors off and make the signal stronger without breaking the rest of the components. Is this possible? Also why are the non-trimming capacitors needed? I have a picture attached. Thank you!
31. ### How to attach wheel to axel? and how to choose motor

I need to know how to attach a wheel to an axel, but first of all, i need an axel with a gear pre-built into it. The axel needs to be over 20 inches long (because that is the width of my vehicle) and support bicycle/tricycle wheels. Does anyone know of such wheels and axels? (The wheels have...
32. ### Difficulty with band type brake

Homework Statement [/B] What is the brake torque and the needed force to stop the drum. Photo of problem: https://gyazo.com/5c814dc6791b29362cc2835dacf7005a Data not on photo: Max pressure is 0.7MPa and friction coefficient is 0.2. Homework Equations T=(P1-P2)D/2 p=2P/bD dP-fdN=0 dN=Pdθ The...
33. ### B Calculating Speed and Distance for a Pneumatic Tricycle

Hello. I am working on planning to build a small pnumatic tricycle. I got far in my calculations, but not quite finished because I am stuck. If someone could check my math, that'd be great, but my problem starts at the second line. ______________________________________________ 1. Let's say...
34. ### Which difficulty level would this problem be considered?

https://www.physicsforums.com/threads/discriminant-of-cubic-equation-in-terms-of-coefficients.715480 The thread is really old and didn't want to post this trivial question in there. The problem is: A cubic equation x³ + px² + qx + r = 0 has three different roots x1, x2, x3. Find...
35. ### Difficulty understanding evolution

Hi I am and athiest and I believe on evolution, but there is an aspect of it that I can't get to grips with. We know evolution doesn't have a conscious mind and that it is the natural blind process of survival of the fittest, based on mutations over generations that are useful to the species...
36. ### Studying Difficulty of other topics in physics

I noticed that rotational/gyroscopic motion in Classical Mechanics is by far more difficult than anything I've seen in E&M. I mean I remember way back in undergrad, I spent more time on it than almost the whole course of E&M combined. Perhaps it's due to the fact that there are an infinite...
37. ### Difficulty proving a relation is an equivalence relation

Homework Statement Homework Equations I don't think there are any in this case The Attempt at a Solution I know that in order to prove R is an equivalence relation, I'd have to show that it is Reflexive, Symmetric, and Transitive. I'm not sure why, but I'm finding this a bit difficult in...
38. ### Testing Difficulty with Modern Physics Midterm

I am currently in Honors Physics 3 which is the third introductory course of my physics degree program and covers modern physics beginning with special relativity. So far we have covered Lorentz transformations and velocity additions, relativistic energy and momentum, blackbody radiation, photon...
39. ### Having difficulty in understanding vertical circular motion?

I am having trouble understanding the concepts of vertical circular motion , though I solve all the numericals , but I think I am lacking the basic concepts of VCM. Explain how I can master this topic?
40. ### I Difficulty with distribution functions

My undergrad probability theory course just got to random variables and distribution functions. Up until this point, the material was very straightforward and I could understand what was being done, but I feel that I am just not seeing the jump between probability with sets and probability with...
41. ### I Difficulty with function dependencies f(u,x)

If you have a function x = x(u,t) then does u necessarily depend on x and t? so u = (x,t) For example, if x(u,t)=u^2 t it seems that because t=x/u^2 , t=t(x,u) I am having difficulty working out the general equation for dz \over dx if z=z(x,y,t) x=x(u,t) y=y(u,v,t) The chain rule...
42. ### Studying Kleppner and Kolenkow difficulty

So I have just started my freshman year at college, and I am majoring in physics. For the introductory sequence on mechanics, we are using Kleppner and Kolenkow. After reading the first section on vectors and kinematics, I feel as though I completely understand the material; however, when it...
43. ### Courses Regarding the Difficulty of Math Graduate Courses

Dear Physics Forum personnel, I will be taking my first graduate course (as an undergraduate) in mathematics starting on this Fall Semester. The course is about the algebraic topology (Hatcher, Spanier, Massey, etc.), which I am very excited to take as I love the topology. I am curious about...
44. ### I Solving Mass-Speed Relation Proof Challenges

I have a hard time understanding the variation of mass with velocity, more precisely the proof. In almost every material I've found, the author analyses 2 bodies colliding. The idea of looking at the collision is not hard to grasp and by considering one of the velocities equal zero, you get a...
45. ### A Difficulty in understanding contracted Bianchi identities

I am confused about the contraction in the proof of the contracted Bianchi identities in https://en.wikipedia.org/wiki/Proofs_involving_covariant_derivatives from the step {g^{bn}}(R_{bmn;l}^m - R_{bml;n}^m + R_{bnl;m}^m) = 0 it seems that the following two quantities are equal...
46. ### Difficulty in understanding graphs in kinematics

I am having a great difficulty in plotting, understanding & visualising the graphs, which is important aspect in physics. So I want some help from everyone to please show me, how to understand a given graph better & juice out everything which it wants. I want to make my fundamental strong by...
47. ### 2nd degree equation difficulty

Homework Statement [/B] Solve without external aids. You may use memorized 2nd degree equation formula. 9(x-2)= 3x(x-2) Homework Equations 3. The Attempt at a Solution [/B] Use memorized 2nd degree equation formula 9x-18= 3x^2 -6x ]]] + 18 9x= 3x^2 -6x +18 ]]] -9x 0 = 3x2-15x + 18...

50. ### Math and physics difficulty level

How hard is college math?Is it beyond senior grade math?Mathematical analysis is one of the hardest discipline in all history or is it physics?Do you have a chance to pass the exams for the disciplines math and physics if you finished a tehnological high school?Can you face college with fewer...