Moments Definition and 626 Threads

Moments (stylized MOMents) is a Filipino celebrity talk show hosted by Gladys Reyes and aired on Net 25. It is a show for mothers and kids that feature the different bonding moments, child-rearing styles and the many facets of motherhood. It airs 7pm every Saturdays with replays on Mondays to Fridays at 10 A.M and Sundays at 11:30 AM / 12:30 PM.

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  1. T

    Confused with the principles in Vector Moments - with Pictures

    Please use zoom function for better view. I'd highly appreciate it if you could also add a diagram on your explanation. Thanks!
  2. S

    Trouble Understanding Bending Moments?

    I'm having trouble fully understanding bending moments. I get the calculations, the force times distance (lever arm), and how to calculate the bending stress (M*y/I). Its the orientation/direction that I am having trouble picturing in my head. I know this is pretty basic, but I just haven't...
  3. S

    Calculate Maximum Bending Moments & Stress

    Can anyone help me calculate the maximum bending moments and maximum stress for the figure i uploaded please.
  4. Femme_physics

    Can you do sum of all moments on a point that's not a rotational axis?

    Can you do "sum of all moments" on a point that's not a rotational axis? For instance, in this structure, with the two wires holding the beam http://img228.imageshack.us/img228/3687/twowiresj.jpg Can I do sum of all moments on B? Or is it not allowed because it's not a pivot point?
  5. D

    ANSYS Bending Moments Calculation

    Dear All, I have been trying to calculate the bending moment redistribution on continuous, steel fiber reinforced, beams. The idea is simple, introducing to the ANSYS model elements, with lowered E-modulus, according always to the evolution of the cracking observed on the actual tests...
  6. Femme_physics

    Solving the Mystery of 3D Mechanics: Is the Sum of Moments 0?

    I recently fall upon this principle while trying to do this 3D mechanics exercise. http://img193.imageshack.us/img193/1416/legitwheel.jpg Looking from a side view (only z and y axes), this should be about right: http://img28.imageshack.us/img28/5758/momentsq.jpg Ignore the question marks...
  7. S

    Raw moments of Gaussian Distribution

    I'm wondering if there was a table of moments for a Gaussian Distribution, I found one up to the fourth moment U \sim N(\mu, \sigma^2) E[U^2]=\mu^2+\sigma^2 E[U^3]=\mu^3+3\mu\sigma^2 E[U^4]=\mu^4+6\mu\sigma^2+3\sigma^4 I'm doing a problem right now and i need the 8th moment.
  8. B

    Calculate Bending Moment of Wooden Joist - 1.0 & 2.0 m

    3) A wooden joist of rectangular cross-section spans a gap of 5.0 m and supports a load of 30 kN placed 3.0 m from the right-hand end. The joist has a depth of 150 mm and the maximum tensile strength that it is allowed to withstand is 12 MPa. a) Calculate the bending moment 1.0 m and 2.0 m...
  9. O

    Second moments of area Izz and Ixx

    Homework Statement A vertical column has the horizontal cross sectional area shown in the attached image. The column carries a vertical compressive point load of 30kN applied at d. calculate the following: a) The second central moments of area IZZ and Ixx b) The maximum values of...
  10. F

    Conditionnal moments of a normal distribution

    Homework Statement We have Vx,Vy following a Normal standardized distribution from which we construct the following correlated variables: X, Y. We consider the events such that x(belong to)A, with 0 < Pr[x(belong to) A] <1. We want to compute V(Y|X E A), Cov(X,Y|X E A) in order to compute...
  11. R

    Calculating Bending Moments Along a Beam

    Homework Statement Calculate bending monents at 1m intervals along the beam Homework Equations The Attempt at a Solution I'm not sure where to start really? I think this is nearly there? Ma = 0 M1 = -5 x 1 M2 = (-5 x 2) + 26.7 M3 = (-5 x 3) + 26.7 - 10 M4 = (-5 x 4) +...
  12. R

    Speed as a ratio, but what about work done and moments?

    Hi all, Speed is a ratio of the distance traveled per unit time. But what then is work done and moments? For example, work done is force multiplied by the distance traveled in the direction of the force. But how would you explain the rationale of multiplying these two quantities? As...
  13. Q

    Solving LTcos(a)= (L/2)mg: Find T=16

    if i take moments at point O, does it mean that LTcos(a) = (L/2) mg and hence T = 32? but answer is 16. what am i missing out here? thanks!
  14. ?

    What Is the Difference Between Moment and Bending Moment in Beam Calculations?

    Hello, I have a small question about moments and bending moments. So, if I have a beam with a loading given by q (N/m) which is given as a function of x then what do these calculations get me? \int xq(x) dx \int (\int q(x) dx) dx The first integral gives me the moment about a point because I...
  15. M

    What Happens When a Child Walks on a Plank Supported by Pillars?

    Homework Statement A 5m long uniform plank of mass 8kg is supported by two pillars at 0.5m and 3m from the left hand end. a 20kg child walks along the plank towards the right hand end. calculate 1. the position the child ia at when the plank begins to tip 2. the forces exerted by the...
  16. F

    Force to topple a block. (moments, centre of gravity)

    Hi I would greatly appreciate help on this problem. Homework Statement Ok so here is the problem Homework Equations The Attempt at a Solution I first tried to work out the moments for the block on the ground with no angle to the ground. moments about a = .45(35000*g) -...
  17. G

    Understanding Dipole and Quadrupole Moments for Energy Calculation

    hi i have two questions :smile:, that i cannot solve by my own: does anybody know how to calculate the potential energy of two quadrupole moments that are separated by a distance r?( i looked for it in all my physics books, but i did not find anything at all) and: if you have two...
  18. G

    What Are the Moments and Products of Inertia for a Rotating Particle?

    Homework Statement A particle of mass m is located at x=2, y=0, z=3. (a) Find its moments and products of interia relative to the origin. (b) The particle undergoes pure rotation about the z axis through a small angle α (see the attached figure). Show that its moments and products of...
  19. N

    Reaction forces in simple beam involving applied moments

    Homework Statement Homework Equations The Attempt at a Solution The problem I'm having is that I'm not sure how to work out the reaction forces because of the applied moment of 50kN.m. I know that the formulas are the sum of forces in a single direction equals 0 and the sum of...
  20. G

    Potential energy of quadrupole moments

    hi i am looking for an equation that gives me the potential energy of 2 quadrupole moments and their mutual distance is assumed to be large. and they have no total charge or dipole moments. does such an equation exist?
  21. L

    Area Moment of Inertia & Stability of Floating Bodies

    Just totally confused which value to use to get the area moments of inertia with this question The ship was initially looks like this the mass of the ship is 5000 tonnes two heavy cargocontainers each of mass 73,370 Kg each assume that the ship has a rectangular waterline area, with length...
  22. H

    Parallelogram Rule for combining forces (moments)

    (2 dimensions.) Given 2 forces acting on an object (not modeled as particle), you can project their lines so that you can find a point of intersection - X. On this point of intersection exists no moment caused by the 2 forces since the line action makes 0 degrees with the forces. It follows that...
  23. M

    Why do we use negative signs for clockwise moments in torque calculations?

    I'm stuck on this problem at the moment. The answer is 19.08 nm clockwise but i just don't see how it can be. Check this. 2.8x(0.8+5.5)= 17.64 nm If I use the 4.6 it ends up 4.6x(0.8+5.5) = 28.98 nm I don't get how it can be 19.08 clockwise when there is only one force going...
  24. A

    Combined direct stress and bending moments

    Hi. I was assigned this coursework by my lecturer. The problem is I have only been taught how to analyse a solid beam section and not a hollow section as is shown in the problem. What I would like to know is how to calculate the area. Usually I would do this by calculating Length x Breadth. I...
  25. D

    Finding Moments of Normal Distribution with Unknown Constant

    Homework Statement You have i.i.d. random variables X1,...,Xn ~ Normal (\Theta,c^2*\Theta^2), where "c" is a known positive constant (relative variability = std. dev(X)/E[X]) and \Theta is an unknown positive constant. Find the first four moments. E.g E[Xj] where j=1,2,3,4.Homework EquationsThe...
  26. D

    Help with Bending Moment Diagrams

    Bending moments Help! Hi guys, didnt really know how the layout of a bending moment diagram would fit under the standard template provided so i'll have a bash at explaining the problem. On my school course i have been doing bending moments/diagrams and shear force diagrams, but a few days...
  27. T

    Calculating & Using Bending Moments: Cantilevers vs. Euler's Strut

    Would anyone be able to explain how to calculate and use bending moments? I have been studying cantilevers and Euler's strut and I don't understand the following: Why for a cantilever the bending moment is positive, and for the Euler strut the bending moment is negative. As far as I can tell...
  28. U

    Are Fixed Beams and End Moments Causing Deflection in Simply Supported Beams?

    I posted this as a part of a thread on the classical physics forums, but the doubt wasn't resolved, so I thought this might be a more appropriate place... A fixed beam is considered equivalent to a Simply supported beam (SSB) with a point load at its mid point(and thus having reactions Ra*...
  29. Y

    Moments problem HELP IM SO LOST

    Homework Statement ive been trying to figure our this mechanics question and I am rather stuck but unfortunately i haven't had much experience with moments find the normal forces applied to the installed stud at points A and B [PLAIN]http://img851.imageshack.us/img851/1826/photoc.jpg...
  30. J

    Understanding Shear and Bending Moments in Beam Analysis

    I have the solution's manual for this particular problem, but I'm having hard time understanding the steps they've taken. I've attached pictures of the problem below. For the shear, are they using 1/2*x*(wx/L) because it is equal to the area of the force? And for the bending moment, where are...
  31. S

    Multivariate Distributions, Moments, and Correlations

    So if I start with a multivariate distribution f(x,y), I can find the marginal distributions, the conditional probability distributions, all conditional moments, and by the law of iterated expectations, the moments of both X and Y. It seems to me that I should be able to relate the conditional...
  32. D

    Mass, Moments and Center of Mass

    Homework Statement A square plate with edge a cm and areal density kr g/cm^2, where r is the distance (in centimetres) from P to one of the diagnals of the square. Find the mass. The Attempt at a Solution I know my diagram is wrong, and I know what the correct one looks like. However, I...
  33. Z

    Question regarding Moments of forces

    Hi I have a question regarding Moments of forces When in equilibrium we have a lever hinged at B which is in between A which is 120' to B and C which is Flat .. A force is applied to A at 50'(P) and another force to C at 70'=100N So breaking down P into components you get P Sin 50 (perp to A)...
  34. N

    Moments Rigid Bodies: Understanding x-axis Forces

    This is not really a homework question but i am having dificullty visualizing the problem and needed some help understanding, the solutions say " The moment about the x-axis due to the forces can be found using the z components of each force acting at their interesction with the xy plane (A &...
  35. M

    Image Analysis - second order moments - ellipticities

    There seems to be a good source here: http://www.cs.cf.ac.uk/Dave/AI2/node194.html But my problem is understanding the summation. What I am trying to do is calculate ellipticites and orientation angles of images using their second order moments of inertia. My images are in matrix...
  36. J

    Forces and Moments: Solving Homework Equations

    Homework Statement A triangular plate is attached to a wall by two pins A and B. It is loaded at point C by A force F Homework Equations Sum of Moments = 0 Sum of Forces = 0 The Attempt at a Solution Moments act around bottom of plate F*L1=L2*Fa+L3*Fb Vertical Forces...
  37. B

    'Reversing' a moments calculation

    http://homepage.ntlworld.com/russelliott/shifting-cofg-1.png A rigid weightless beam is supported on 3 springs, spaced as marked. The forces in the 3 springs are initially equal (at 10N). The position of the 30N balancing force F to keep the system in equilibrium is determined from taking...
  38. Femme_physics

    Is my diagram correct? If so, have I made the moments equation correctly?

    Homework Statement Through pulley B, set upon structure ABC, a mass (m) of 2 tons is being lifted in constant velocity. The beam AB is horizontal. Calculate the reaction forces at the beams. Ignore friction at pulley. http://img225.imageshack.us/img225/4750/236shrinked.jpg...
  39. T

    Projections of Moments on a new Axis

    Hi all, this is my first post, so forgive me if this is in the wrong forum. (I believe it does belong here) We are currently doing moments in physics and I have seen this in a few homework problems but can't seem to grasp it. For example, in one question, we are given a new axis AA that...
  40. R

    Understanding Shear and Moments: Signs in Cantilever Beam

    I can't seem to wrap my head around the signs of shears and moments when applied to beams. Consider a cantilever beam that goes from x = 0 to x = L (with positive deflection, or y(x), corresponding to a deflection upwards). The standard equations tell us that \text{Moment} = EI...
  41. R

    Mechanics question - Forces & Moments

    Homework Statement http://img262.imageshack.us/img262/4343/scan22.png The Attempt at a Solution For the first question my attempt was: [PLAIN][PLAIN]http://img255.imageshack.us/img255/2628/screenshot20110110at182.png But this is wrong. The correct answer for part a was...
  42. H

    Moments of Inertia Homework: Find Max Height H

    Homework Statement part a) A block of mass m slides up an incline with an initial speed v0. The incline is on an angle, &theta;, and block stops sliding at height H. -If the incline is frictionless, determine the max height H to which the block will rise, in terms of given quantities and...
  43. L

    How to Calculate Potential Energy Difference for a Dipole in an Electric Field?

    Homework Statement A molecule of water has a dipole moment of 6.1×10–30 C m. Calculate the difference in potential energy between when its dipole is parallel to an electric field of 2.0×105 V m–1 and when it is anti-parallel to the field. Homework Equations U=kq1q2/r V=U/q V=Ex...
  44. I

    Turning effect of forces - moments

    Homework Statement A uniform board is hinged at A and supported by a vertical rope at P, 6.0m from A. A man of weight 700N stands at the end of the board at point B, which is 15.0m from hinge A. If weight of board is 50N,calculate the tension T in the rope.Homework Equations By principle of...
  45. T

    Beam deflection (area moments)

    just started looking at area moments. question i am stuck on is below. use the area-moments to calculate the mid span deflection produced by the given loadings, showing clearly all steps in the method and calculation: support condition: simply supported span: 7.20m section: 406x140x39...
  46. P

    How Do First Class Levers Apply to Scissors?

    I understand the principle of moments and how it is applicable to first class levers: A stone, at 1 m from the fulcrum weights 300N I stand at 3 m from the fulcrum: Clockwise Moment = Anticlockwise Moment F x 3 = 300 x 1 Therefore, I have to exert 100N of force to lift the stone. To...
  47. T

    .Calculating Reaction Forces and Moments for 3 Pin Frame ABCDE

    A 3 pin frame ABCDE is supported at A and E. it supports vertical loads of 60 kN at B 80 kN at c and 100 kN at D as well as a horizontal UDL of 50kNm along DE. Calculate the reaction forces. I have REV = 124 kN and RAV = 116 kN. REH = 115.3kN and RAH = 215.3 kN. Are these correct Next...
  48. G

    Why Do Principal Moments of Inertia Values Change with Different Origins?

    Consider 4 equal masses at the 4 corners of a square of side b. First I took one of the corners as the origin and found the principal moments of inertia to be Ixx=mb^2, Iyy=3mb^2, Izz=4mb^2 after solving the secular equation. Again, I found the principal moments of inertia but now with respect...
  49. G

    Why do different origins result in different principal moments of inertia?

    Homework Statement When I try finding the principal moments of inertia with respect to different origins for any arbitrary configuration(assuming that the inertia tensor is diagonalized), I end up getting different values. Intuitively, this is quite acceptable because the mass distribution is...
  50. G

    What could be wrong with my approach to finding principal moments of inertia?

    Homework Statement I have a question on finding the principal moments of inertia of a discrete set of mass points on a plane. If I choose one of the mass points as the origin, I always end up having a diagonal matrix for the inertia tensor for any configuration. Isn't that weird? I sense...
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