Moments Definition and 598 Threads

Hi Why does a bond stretch or vibration have to cause a change in dipole moment to be IR active? Presumably all vibrational modes depend on energy aborption to occur whether they cause a change in dipole or not. I'm presuming that only those vibrational modes that cause a dipole change are...

Homework Statement Hello Every one, well i have a question regarding the Fixed End moments, if we had a Horozontally Fixed End supported Beam, with equally distributed load (W) on the beam, and we require the moment at the fixed Ends, which Equation would i use: Homework Equations 1...

Homework Statement I have attached the problem in one file and I have attached my attempt in the second file. I only need help deriving the moment of inertia for the first (1) and fourth (4) objects but I have attached my solutions to the other objects in case it helps jog someones memory...

What is the common origin of the terms: (1) "moment" as in "moment of interia" (2) "moment" as in the math terms first moment, second moment, etc. (3) "momentum"? The first two are somewhat easy to see, though I'd like see someone familiar with it spell it out. But I've always wondered...

Homework Statement A uniform metre rule of mass 100 g is supported by a knife-edge at the 40 cm mark and a string at the 100 cm mark. The string passes round a frictionless pulley and carries a mass of 20 g as shown in the diagram. At which mark on the rule must a 50 g mass be suspended...

1. 1. Homework Statement Ok. I'm given a force diagram, and I have to figure out the reaction forces at the two points on the ground. answer key: (498.1N↑; 104.2N→, 92.8N↑) Homework Equations Ok. I only got so far as the x-reaction force at the pivot... 600 sin 10 = <- 104.2N...

Can anybody tell me what a couple is. From what i gather it is when two forces are equal, opposite and parallel. But but if 1 force is bigger than the other say a 2 and a 3N force could it be said that there is a couple of 2N forces ? Does it have anything to do with moments? __________ Daniel

Homework Statement A metre rule is balanced at the 50 cm mark. If a mass of 5kg is placed 40 cm from the pivot at one end, what mass must be placed 30 cm from the pivot on the other end to balance the rule? Homework Equations M1 * G * D1 = M2 * G * D2 The Attempt at a Solution...

Skip to the bottom for the short version... We are learning moments in statics currently, and I have a problem that asks me to resolve the force given into x and y components, then, using "the principle of moments" aka Varignon's Theorem, find the moment with that same force applied at...

Homework Statement The tower is 70 m tall. If the tension in cable BC is 2 kN, and you want to adjust the tensions in cable BD and BE so that the couple exerted on the tower by the fixed support at A is zero. A) Determine the tensions in cable BD and BE by applying the sum of the...

Homework Statement A uniform 10 m long, 50 kg pole is lying on the ground. You get your little brother to lift at one end with an upward force of 100 N. How far from the other end will you need to lift so the pole stays horizontal (in m)? [Hint: Using your little brother as the fulcrum, what...

if i have a fixed x and y-axis and i have a few forcesin both negative and positive directions when i calculate the sum of the moments how am I meant to know which direction they act M=Fd

Homework Statement The 4-kN force F is applied at point A. Compute the moment of F about point 0, expressing it both as a scalar and as a vector quantity. Determine the coordinates of the points on the x- and y-axes about which the moment of F is zero Homework Equations m=fd The...

Homework Statement Hi there, I am kind of new to this site, so please bear with me. On the more advanced physics forum page, there was a question about dipole moments, and the way the help had been described was a bit over my head. I am posting this for clarification purposes because this is...

Homework Statement I have a problem which involves me drawing the bending moment diagram for a trapezoidal distributed load. I understand the bending moment diagrams for a uniform distribution, and partially for a triangular distribution, however i am struggling to link the two for a...

Homework Statement The diagram (not included) shows a straight, horizontal swimming bath spring board of length 4m and weight 300N. It is freely hinged at A and rests on a roller at B where AB=1.6m. A boy of weight 400N standard at end C. a) show directions of forces acting on A and B b)...

QUESTION 1 WORK TO SOLVE QUESTION 1/SECTION1 - CONFIDENCE 80%

Homework Statement A smooth uniform rod AB, of length 3a and weight 2w, is pivoted at A so that it can rotate in a vertical plane. A light ring is free to slide along the rod. A light inextensible string is attached to the ring and passes over a fixed smooth peg at a point C, a height 4a...

Homework Statement A horizontal piece of wood that has a weight 40N is held in equilibrium by two brackets, A and B. The wood is 1.6m long (CD). A is 0.4m from C and B is 0.2m from D. Meaning that there is 1.0m between A and B. At rest the reaction force at A is 24 N and at B 16N. When an...

Homework Statement A plank of wood is lifted off the ground so it has one side on the ground (A) and the rest of the wood at a slope at 15degrees to the horizontal. The length of the wood (AC) is 2.5m. A force is applied at C at 65degrees to the horizontal to the left keeping it in...

1. Calculate the total moment of the forces on the thin beam shown in the attached file, about each of the points A, B, C, D, E. Each of the distances AB, BC, CD, DE is 1m. 2.Clockwise moments = Anit-clockwise moments 3.(Axd)+(Exd)+[50sin(45)]=(20xd)+25 20+20+42.5=20+25 82.5=45...

1. The rod shown in the diagram(mass 10g, length 100cm) is in equilibrium. Find the position of the pivot and the magnitude of the supporting force F. 2.clockwise moments = anti-clockwise moments 3. I'm not so sure here. I have unknown distances. Please see file attachment 2 -...

Homework Statement How do you find the tensor of inertia for fractions of the usual volumes? (like half of a sphere, half of a cylinder, half of a disk, quarter of a disk, etc.) I already know the tensor of inertia for the whole volume. Take M as the fraction of the volume's mass, not the...

Is there someone who can provide me with a link that clearly states the best way to tackle these problems? Your help would be greatly appreciated.

Homework Statement I linear spring has one end attached to a ceiling, the other end hanging freely. It was noted that the spring was extended by 120mm when a mass of 2.5kg was attached at the bottom. If the moment of inertia of the mass is 10kg.m2 about its vertical axis, calculate the...

Is there a reason the moment of inertia is called the "moment" of inertia? A while back, for whatever reason, I remembered how the moment of inertia is formulated and I realized it had similarities to the e/m moments; that is the integration of the mass density multiplied by coordinates. In...

I am trying to understand how the concept of moment was introduced in physics. For example I don't understand how the formula of the moment of impulse was created. Specifically I don't understand why the multiplication with R (L=PXR, or torque=FXR). Is it demonstrated by experimentation, or the...

i want to learn about magnetic dipole moments but don't have a good grasp on it

Hi, I am creating an helicopter simulation and have a question about calculating the correct helicopter origin of moments. In its simplest terms, ignoring drag and tail rotor forces and torques I have the main rotor generating an upward thrust from the rotor hub, and gravity generating...

Hello I'm new :) I'm stuck on my assignment on moments. Homework Statement Now i have attached a copy of my assignment paper which I scanned. Here is the link Now the horizontal and verticle forces sum is correct. But when I try to do the sum of moments I get 50.831 Kn when the...

Problem: Find the principal moments of inertia of an ellipsoid. I began to label moments of intertia about minor axises. But I'm not sure where to go after that.

Homework Statement Hey all I have a physics problem that I need some help setting up the problem: A bar of length 2L rotates with angular velocity \omega, which points in the +y direction. The bar makes an angle \alpha with the y axis, with its centre corresponding to the origin. The bar...

Homework Statement Four masses are held in position at the corners of a rectangle by light rods.Find the moment of inertia of the system about the x axis.Find the moment of inertia of the system about the y axis.Find the moment of inertia of the system about an axis through O and...

Hi, I need some guidance regarding this exercise, Homework Statement Calculate The Moments about the Point A I attached the visual representation of the exercise, it has common A(PIN)---------B(ROLLER) element, then two forces going down( 5 Kips & 2 kips ), then the distances about...

how are weights distributed on a beam

Can someone give me an example where we have \mathbb{E}z=0 , \mathbb{E}z^2=1 (i.e. finite expectations) BUT, \mathbb{E}z^4= \infty ? Also, I cannot think of a case where: \mathbb{E}x=\infty where x>0 BUT, \mathbb{E}| \log x |< \infty Thanks in advance

1. Find the moment of inertia I_x of particle a with respect to the x-axis (that is, if the x-axis is the axis of rotation), the moment of inertia I_y of particle a with respect to the y axis, and the moment of inertia I_z of particle a with respect to the z axis (the axis that passes through...

Homework Statement The cup shown in the picture is filled with 6 oz of coffee. The center of gravity is located at G. If a vertical force is applied to the rim of the cup a shown in the picture, determine its magnitude so that the cup is on the verge of tipping. Homework Equations sum...

Determine the moment created about the support leg at "A" caused by the tension in the cable of 12.3kN. (see attachment for diagram)

Homework Statement I am in my second year of mechanical engineering. This is a statics problem i would like help starting http://img230.imageshack.us/img230/9501/hw1z.jpg Homework Equations The Attempt at a Solution I know I need to calculate the force time distance but...

Hi, all, Let's assume a random variable's variance is zero as sample size tends to infinity somehow, can I say that its higher order central moments are also zero as the sample size tends to infinity? Thks a lot

Homework Statement [PLAIN]"[URL=http://img193.imageshack.us/my.php?image=63378846.png[/URL] Fig.A shows the balanced position of a light rod carrying an object X and a mass M . Fig.B shows the balanced position of the same system when X is immersed in water.If the density of water is d,the...

\vec{J} - mechanical moment \vec{L} - orbital moment \vec{S} - spin moment \vec{J}=\vec{L}+\vec{S} When can I say J^2\approx J(J+1) L^2\approx L(L+1) S^2\approx S(S+1)?

Homework Statement "In raising the pole from the position show, the tension T in the cable must supply a moment about O of 72 Knm. Determine T." Homework Equations M = Fd The Attempt at a Solution d = 12sin(30) = 6m T = 72/d ==> 12m I do not know what I am doing wrong...

Ok, so for equilibrium (no moment about any point), all the lines of action must pass through a single point right? But what about a plank, balanced at its centre, with forces on both sides of the plank so the forces are in equilibrium, and there is no moments also. But what about the line of...

Homework Statement A vertical sluice gate is 5 meters wide and 3 meters deep. calculate the resultant thrust and overturnning moment when the water is level with the top edge of the gate. Density water = 1000kg/m^3 Homework Equations Newton's First Law F = ma Moment = Force x...

Hello, in statistics, one can derive the moments of a distribution by using a generating function <x^n> = \int dx x^n f(x) = \left( \frac {d}{dt} \int dx \exp(tx) f(x) \right)_{t=0} = \left( \frac d {dt} M(t) \right)_{t=0} Is there a similar method to derive the multipole moments in...

Hi, I'm trying to use moments to find the mean of a pdf. Here is the pdf: f(x|\theta) = 2 \theta^{-2}x^3 exp(\frac{-x^2}{\theta}) I'm not really sure where to start. I can multiply the pdf by X and then integrate with respect to X, but it gives me the wrong answer. Any ideas...

Homework Statement Calculate the magnitude of the bending moment and shear forces at the centre of the beam shown in the attached figure Homework Equations The Attempt at a Solution For the shear forces I think its the sum of the vertical components, Bending moment = not...

Homework Statement http://i277.photobucket.com/albums/kk63/sarcasticlil123/truss.jpg Homework Equations p1=800#, p2= 600# and a=8, determine a reaction load The Attempt at a Solution sum Ma=0=-4.5p1-6p2+12.5cy I am generally lost, this isn't homework its practice for the final...