What is Joint: Definition and 326 Discussions

A joint or articulation (or articular surface) is the connection made between bones in the body which link the skeletal system into a functional whole. They are constructed to allow for different degrees and types of movement. Some joints, such as the knee, elbow, and shoulder, are self-lubricating, almost frictionless, and are able to withstand compression and maintain heavy loads while still executing smooth and precise movements. Other joints such as sutures between the bones of the skull permit very little movement (only during birth) in order to protect the brain and the sense organs. The connection between a tooth and the jawbone is also called a joint, and is described as a fibrous joint known as a gomphosis. Joints are classified both structurally and functionally.

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  1. annanause

    Elbow joint and vertical force

    Homework Statement State an expression for the vertical force at the elbow joint FE in terms of the other forces acting when the arm is held horizontal with the dumbbell in the hand. Homework Equations No equations needed. The Attempt at a Solution Since muscles can not expand beyond...
  2. S

    Statics: 2 shafts interconnected by a universal joint

    Homework Statement I got part A of the problem right. I am stuck on part B. As you can see, they ask for the reactions at B, D and E.[/B]Homework EquationsThe Attempt at a Solution OK, here's the book's the answers: at D, 350N k. At E, -100Nk, and at B -250N k. So, we have a 50Nm torque...
  3. L

    Programs Joint Degree in Computer Science and Physics.

    Hello,I just graduated from high school and i will be starting university in fall 2016 at the University of Manitoba in Canada. They have a joint degree program in physics and computer science which is a program I'm considering since, I enjoy studying about both disciplines. I would like your...
  4. R

    I Joint Density of (X,Y) from R_PDF(r),V_PDF(v)

    For random variables (X,Y) = (R*cos(V),R*sin(V)) I have R_PDF(r) = 2*r/K^2 and V_PDF(v) = 1/(2*pi) where (0 < r < K) and (0 < v < 2*pi) Is XY_PDF(x,y) the joint density of X and Y that I get by using the PDF method with Jacobians from the distribution R_PDF(r)*V_PDF(v)? So without having...
  5. BobTheFrog

    Plagiarism in joint lab report

    Not so much homework question, more about experience doing homework. You have likely had experience writing lab reports quite long. I have a partner and I am worried that he is doing what my university would consider plagiarism. I've asked him about it and got nothing back. To give context he...
  6. Guest312

    Optimizing Movable Joint Parts for Slider Crank Mechanisms

    I want to make a simple slider crank mechanism. I don't know what type of bolts or whatever is used for movable arms. I've heard online so far that using a carage bolt and nylon lock nut will work, but I bet there's probably other ways to make a movable joint. Something more secure. I'm sure...
  7. T

    How can i solve joint proportion?

    I am currently doing aops introduction to algebra book and I can't figure out how to solve joint proportion or some ppl call it joint variation. I don't which values should i substitute for the formula, z=kxy. I don't which value should i substitute into z to the word problems. I can get through...
  8. Y

    MHB Joint distribution of a discrete random variable

    Hello all I have this question I am trying to solve. In an urn there are 6 balls, numbered: 1,2,3,4,5,6. We take 4 balls outs, without replacement. X - the minimal number we see Y - the maximal number we see I need to joint distribution. I understand that X is getting the values 1,2,3 while...
  9. Linder88

    Conditional probability with marginal and joint density

    Homework Statement Determine ##P(X<Y|x>0)## Homework Equations X and Y are random variables with the joint density function $$ f_{XY}(x,y)= \begin{cases} 4|xy|,-y<x<y,0<y<1\\ 0,elsewhere \end{cases}$$ The marginal densities are given by $$ f_X(x)=2x\\ f_Y(y)=4y^3 $$ The Attempt at a Solution...
  10. Linder88

    Joint cumulative distribution function

    Homework Statement Compute the joint cumulative distribution function $F_XY(x,y)$? Homework Equations The marginal distribution function $F_X(x)$ \begin{equation} F_X(x)=P(X\leq x)= \begin{cases} 0,x<0\\ 0.6,0\leq x<1\\ 1,x\geq 1 \end{cases} \end{equation} and $F_Y(y)$ \begin{equation} F_Y=...
  11. W

    Gyroscopic/Self balancing Mechanical Ankle Joint

    Hello. This is the first post on this site I'm making outside of the "New member welcome" part, and I intend on getting right down to why I'm here: I would like to know of any possible designs or methods by which to build a mechanical ankle joint capable of holding at least 500 US pounds, and...
  12. T

    Joint probability distribution

    Homework Statement The joint probability density function of X and Y is given by f(x,y)=(6/7)(x^2+ xy/2) , 0<x<1, 0<y<2. (a) Find the pdf of X. (b) Find the cdf of X. (c) FindP(X<.5). (d) Determine the conditional pdf of Y given X = x. The Attempt at a Solution a) the pdf is what is...
  13. T

    Impedance matching between two 50 ohm cables through a joint

    Hi, I'm in a bind trying to determine how to handle impedance matching through a joint of copper wire sandwiched between two 50-ohm coaxial cables (the joint is an interface between atmosphere and a UHV system). There is a signal pulse with a rise time of 2 ns coming through one of the coaxial...
  14. W

    Calculating C and Marginal PDFs for a Uniform Distribution on a Bounded Area

    Homework Statement E = { (x,y) | |x| + |y| ≤ 1} fx,y (x,y) = { c (x,y) ∈ E 0 otherwise } Find C. Find the Marginal PDFs Find the conditional X given Y=y, where -1 ≤ y ≤ 1. Are X and Y independent. Homework Equations I'm taking a guess here in the solution... but F(x,y) = F(x)F(y) and...
  15. T

    Universal Joint Manufacturer/Supplier

    Does anyone know a manufacturer or supplier of joints like the one shown here: https://grabcad.com/library/universal-joint-graphite-bushes The main feature I'm looking for is the counterbores at the ends that allow mounting to a flat plate. Almost all the ones I've found are made for...
  16. W

    Marginal PMG of of 2 random variables with Joint PMF

    Homework Statement Consider two random variables X and Y with joint PMF given by: PXY(k,L) = 1/(2k+l), for k,l = 1,2,3,... A) Show that X and Y are independent and find the marginal PMFs of X and Y B) Find P(X2 + Y2 ≤ 10) Homework Equations P(A)∩P(B)/P(B) = P(A|B) P(A|B) = P(A) if independent...
  17. T

    Joint probability distribution

    Homework Statement 4. Let X and Y have the joint probability distribution (a) Find P(X +Y ≤ 4). (b) Find the marginal probability distributions f1(x) and f2(y). (c) Find P(X < 2|Y = 2). (d) Are X and Y independent? The Attempt at a Solution a) f(1,1) + f(1,2) + f(1,3) + f(2,1) + f(2,2) +...
  18. T

    The Joint PDF of Two Uniform Distributions

    Homework Statement A manufacturer has designed a process to produce pipes that are 10 feet long. The distribution of the pipe length, however, is actually Uniform on the interval 10 feet to 10.57 feet. Assume that the lengths of individual pipes produced by the process are independent. Let X...
  19. stevebenson

    Help identifying this pivoting joint mechanism

    Hello all, I need help identifying the following pivoting joint, and also coming to an understanding of how this particular joint works and is designed... Thanks for your help!
  20. V

    MHB Computing joint cumulative distribution function

    With X having the exponential $(\lambda)$ distribution and $Y = X^3$, how do I compute the joint cumulative distribution function? Here is how far I've come: $F(x,y) = P(X ≤ x, Y ≤ y) = P(X ≤ x, x^3 ≤ y) = P(X ≤ x, X ≤ y^{1/3}) = P(X ≤ min(x, y^{1/3})$, $f_x(x) = \lambda e^{-\lambda x}$$ for...
  21. S

    MHB Joint Probability of Independent Events

    Hello, I'd like someone to double check my maths please, it wasn't the greatest at school and that was a few years ago! If I am incorrect could you please tell me the correct answer as well as show me how to apply it so I can figure out similar problems myself. Thanks. Yes, this is about...
  22. L

    A quick Question on Joint Uniform Distribution

    Hi, I have a quick question. If both X and Y are uniformly distributed on the unit interval [0, 1]. Can we prove that the joint distribution of (X, Y) is uniform on the unit square [0, 1]×[0, 1]? Do we need any condition to ensure the result, such as Independence between X and Y? Thanks.
  23. M

    How do I calculate an area of joint uniform distribution with domain

    This technically isn't a coursework or homework problem: I have a uniform Joint density function for the lifetimes of two components, let's call them T1 and T2. They have a uniform joint density function, both are positive it follows, and the region is 0<t1<t2<L and L is some positive constant...
  24. P

    Gimbal Joint analysis (Thermal expansion)

    Good day, I am currently developing a thermal expansion analysis of a pipe line, I need to validate if the current installed Gimbal joints will withstand those conditions. These gimbal joints just allow angular movement. Is there any software or method that can help me as reference for this...
  25. neosoul

    Getting Accepted into Joint PhD/JD Program

    PF Family, What is a good way to increase my chances of getting into a joint PhD/JD program. I'm physics major with a 3.86 GPA, a rising junior, and have plenty of math electives (if that helps). I am currently in an REU program at my school, and we are doing climate modeling. I am also doing...
  26. D

    Hip joint torque in walking mechanism

    Hi everyone, I am making a hexapod ( six legged walking mechanism ) which walking by keeping 3 alternate legs in air and other 3 on ground, pushing the body ahead, also known as tripod gait. The basic structure of model and one leg are shown in the pictures. I want to calculate the torque...
  27. M

    Solving a Connection Problem: Bolted Joint Stress Analysis

    Hi dear friends. I have a big problem and I need your help, I've realized that the joint connection I've drawn (and it is made already) was (most probably) wrong. There is a plate that is bolted to two U beams and the plate is welded to a horizontal I beam at the top. Please take a look at the...
  28. Lewis7879

    Joint problem density function problem

    I need help guys I can't understand this Can anyone explain thoroughly how do I form the range for this question? f(x,y)= e-x for 0≤x≤y≤∞ 0 Otherwise Find P(x+y≤1) I attempted this by integrating through the range of 0≤y≤(1-x) and 0≤x≤∞ but that...
  29. D

    What are the Properties of Joint Density Functions?

    Hello, Homework Statement The joint probability density function of X and Y is given by f(x,y)=c*1(|y|<x<1) 1 is the indicator function -Find c -Find the marginal densities of X and Y -Find the means, variances and the covariance -Find conditional densities, means and variances of X given...
  30. J

    Can You Share Design Tips for Bolted Joints That Won't Loosen?

    I'm looking for some info/guidelines on designing bolted joints that are made to move with some resistance/friction...all without loosening the bolt. Think of a legs of a camera tripod; the legs can rotate in and out with resistance, but they never loosen. It seems the basic idea is that the...
  31. K

    What is the force at the joint C on the right beam?

    Homework Statement Pay attention that the left support A is a fixed axis and the right, B, is a free moving axis. C is a joint. The left beam (to the joint): 2m, 6[kN], the right beam: 3m, 10[kN]. What is the force F. Homework Equations Moments: ##M=F\cdot L## The Attempt at a Solution To...
  32. S

    How is E(X) = 1 obtained for this continuous joint pdf?

    Homework Statement The problem and its solution are attached in the TheProblemAndSolution.jpg file. Homework Equations E(X) = integral from -infinity to infinity of x * ##f_X(x)## ##f_X(x)## = integral from -infinity to infinity of ##f_{XY}(x,y)## dy The Attempt at a Solution Basically, how...
  33. Z

    Joint probability mass function

    I'm having difficulties reading this, could someone please explain to me? 2 coins Ω = {HH, HT, TH, TT} 0 = Tails 1 = Heads PX,Y(x,y) = P({TT} n {HH}) for (x,y) = (0,0) P({HH, HT,TH} n {HH}) for (x,y) = (1,0)...
  34. C

    Probability Question - Joint density function

    Before I begin, here is the question: If the PDF of two independent random variables X and Y are: f(x) = exp(-x)u(x) f(y) = exp(-y)u(y) Determine the join probability density function (JPDF) of Z&W defined by: Z = X+Y W = X/(X+Y). So, I know how to solve this except for one thing. How do I get...
  35. M

    Ross ch.6 problem 26 Joint Distribution of Random Variables.

    Homework Statement Suppose that A, B, C are independent random variables, each being uniformly distributed over (0, 1). ) What is the probability that all the roots of the equation Ax2 + Bx + C = 0 are real? Homework Equations (b) What is the probability that all the roots of the equation...
  36. 9

    Can a threaded tapped joint function as a friction joint?

    I have a tapped hole. A threaded rod goes through the hole. A single nut secures the threaded rod in position. Only one plate is threaded. Note the clearance hole in the top plate. A picture is attached. A friction joint in a bolt occurs when the clamping force creates a normal force. This...
  37. Cognac

    Conditional probability with joint condition

    So say I have Pr(Z|X&Y) I'm guessing that it follows the standard Pr(A|B)=[Pr(B|A)Pr(A)]/Pr(B) So Pr(Z|X&Y)=[Pr(X&Y|Z)Pr(Z)]/Pr(X&Y)?Also, if X&Y are independent, then would I get Pr(X&Y|Z)=Pr(X|Z)Pr(Y|Z)?
  38. 9

    Modelling a joint in a threaded rod, joint, nut and washer assembly

    I am trying to use computer modelling to see stress. I want to compare it to my hand calculation, which uses the frusta cone method to find the stiffness of the joint. This way, I can check my calculation in a conceptual way. The model includes a nylon insert nut, a threaded rod, a washer and a...
  39. H

    How can Rhino help create a dynamic parade float?

    We are using a childs wagon as the base for a parade float. The float will be decorated to look like a canoe. We want to attach "waves" to the wheels so that they move up and down as the wheels roll down the road. Similar to this...
  40. L

    MHB Joint Probability Density Functions

    Problem: Two birds have landed on a power line that spans the 100' distance between utility poles. a) What is the average distance between the birds? b) The line runs north and south. Another bird lands on the line. What is the expected position of the north-most bird from the south-most...
  41. S

    Joint probability of partitioned vectors

    Hi everybody, I apologize if this question is too basic but I did 1 hour of solid Google searching and couldn't find an answer and I'm stuck. I'm reading Bishop's Pattern Recognition and Machine Learning and in the second chapter he introduces partitioned vectors. Say, if X is a D-dimensional...
  42. G

    MHB Joint Probability Density from two Gaussian Distributions

    I've been reading the following paper entitled "An Improved Algorithm to Generate a Wi-Fi Fingerprint Database for Indoor Positioning": An Improved Algorithm to Generate a Wi-Fi Fingerprint Database for Indoor Positioning In Part 3.3 (Step 6), it states: Use the fingerprint database to...
  43. E

    Bayes rule and joint probability

    I try to understand the following equation but I can not. I have basic knowledge about Bayes rule and joint probability. How can we produce this result? I would appreciate any help. p(R|q,x)/p(NR|q,x)=[p(R|q) / p(NR|q) ] * [p(x|R,q) / p(x|NR,q)]
  44. D

    MHB Continuous joint probability density functions

    Consider the following joint probability distribution function of (X , Y): a(x + y^2) {0<=x<=2, 0<=y<=2} 0 otherwise Calculate the value of the constant a that makes this a legitimate probability distribution. (Round your answer to four decimal places as appropriate.) And then, For the...
  45. E

    For which joint distributions is a conditional expectation an additive

    I know that, for a random vector (X,Y,Z) jointly normally distributed, the conditional expectation E[X|Y=y,Z=z] is an additive function of y and z For what other distributions is this true?
  46. carllacan

    Explicit joint probability distribution.

    Hi! Suppose we have two variables Y and Z that depend on a third one, X. We are given P(x), P(y|x) and P(z|x). The joint probability distribution P(x,y,z), according to the chain probability rule, is given by P(x,y,z) = P(x)P(y|x)P(z|x,y) But how can we compute P(z|x,y) with the given...
  47. R

    What is the Expected Value of Two Random Variables with a Joint PDF?

    Homework Statement two random variables have a join pdf f(x,y)= c , x^2+y^2<= 1, x >0, y>0 0, otherwise Find c. Find E{xy}. Homework Equations The Attempt at a Solution For the first part, since area= pi/4, c(pi/4) = 1 c=(4/pi) b) x=cos θ y= sin θ ∫∫-(sin...
  48. A

    Reaction Forces on a Frame With Roller Joint and Pin Joint

    [b]1. Hi, The problem: A roof support frame has various leadings on it. The frictionless pin joint at points A has vertical and horizontal reaction forces. The rollers at point B allow free movement in the horizontal direction and has a vertical reaction. a/Calculate The total Horizontal...
  49. aladinlamp

    Does this hydraulic part exist? linear retractable hydraulic joint

    hi i am looking for linear retractable hydraulic joint, basically it is hydraulic cylinder with hole in the rod, it does not perform any work, it does not resist the fluid flow, it just expands and retracts as needed, it acts as a hose but its cylinder based is there something like...
  50. stripes

    Finding the joint moment generating function given the joint PDF

    Homework Statement Homework Equations The Attempt at a Solution The problem is the integral is non-elementary, so now what? Part (b) follows trivially from part (a). But is there some kind of shortcut I have to take, because no matter what substitution I do, the integral...
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