Moments Definition and 598 Threads

Hi people, I'm a bit confused as to when we can and cannot add 2 moments together. From what I understand, we CAN add them together if they are both about the same origin but CANNOT if they are about different origins. But when drawing and calculating bending moment diagrams, you have to...

Homework Statement A bicycle of a mass 15kg resting in a vertical position, with the front and back wheels touching the horizontal ground at points P and Q respectively, where PQ=1m. The centre of gravity of the bike is vertically above O, a point on PQ where PO=30cm. Given that the normal...

Homework Statement A lamina has the shape of the region in the first quadrant that is bounded by the graphs of y = sinx and y= cosx, between x = 0 and x = π/4. Find the centre of mass if the density is δ(x,y) = y. Homework Equations I know all the equations for moments and center of...

Homework Statement Hi there - I'm working through a bit of mechanics revision and have been looking at some of my uni past exam papers from a good few years back when the syllabus was different, so I'm not familiar with a lot of the material covered - it's not strictly relevant to my current...

I have been asked to come up with a formula by a rather persistent person who is Addiment that a wheel on an accelerating treadmill attached to a mass (such as a car) would not produce enough translational force to move the Car. The Question as posed to that persons; Please forgive any and...

How do you take the moments of inertia of a flat body? I know howto take it if it's a 3d body. And the 2d case should be really simpe,but I'm too stupid to figure it out. Can you help me? For example.. Say we have a body that's a rectangle of mass m on |x| < a, |y| < b..? Thanks so much.

there are 2 questions which are driving me insane because I jus don't understand what to do! I hope that if someone could go through the questions in detail then I'll finally understand how to go about answering. 5. A rod AB of mass 6kg and length 3m has its centre of mass 1.2m from A. It is...

Hi,I am trying to calculate the end reactions for the beam shown in the diagram attached. I have got this far but know I am going wrong somewhere. To check ,RA + RB should equal the total load,point and UDL so I am told. Can someone point me in the right direction please. Many...

Homework Statement Find the value of the dipole moment of the distribution of charges. -2q on top of equilateral triangle +q on each of the other points. Each charge is separated by distance d. Homework Equations p = \sum (q_i)(r_i) The Attempt at a Solution p =...

Homework Statement I got a problem solving this question. http://img228.imageshack.us/img228/7049/image164.jpg The Attempt at a Solution Im not sure if I am missing a rule here. I take CW to be positive and CCW to be negative. But my attempt to solve it failed =[...

Hello everyone; here is the problem that I’m currently working on: =============================================== a- Find the principal moments of inertia of a flat rectangular plate (mass = 30g, a = 80 mm, b = 60 mm) that rotates about a diagonal with velocity ω = 15 rad/s. b- What are...

Homework Statement http://i124.photobucket.com/albums/p27/lollipopgourmet/untitled.jpg If the couple has a magnitude of M, determine the magnitude F of the couple forces. Since this is an X-Y plane, I assumed the equation would simple just be M=Fd, where I know the moment, and just have...

Homework Statement Find the component forces Az, Ay, Bx, By, Cx, Cz: http://phga.pearsoncmg.com/onekey/web/hibbelerSD10e/Public_Html/chapter05/H-4ed-5-92a-fbd.gif Homework Equations The downward force at the origin is 250 lb and the moment is 25 ft-lb The Attempt at a Solution Well first...

I am trying to determine force X I know it is the principle of moments so I think you use this equarion - not sure though: In equilibrium (the sum of)anticlockwise moments = (the sum of) clockwise moments...

Moments and force couples...confused! Homework Statement I have attached 2 pdfs: 1 is the problem, the second is the solution. I need help understanding the solution. Diagrams included. The gist of the problem: Need to calculate a dimension "a" such that a resultant couple (from 2 force...

I have got myself very confused. I am trying to understand Nuclear Magnetic Resonance but am running into issues. The basic idea of NMR, resonant excitations between Zeeman split nuclear energy states, I understand. The semi-classical picture of precessing moments also makes some sense to me...

Homework Statement I am stuck on question 6c on this paper. Can anyone have a look at it please. I don't know were to start. do I place the rock 'x' meters away from one of the strings and set one of the strings tension to 40g? Homework Equations The Attempt at a Solution

Homework Statement This is a two part question. In the first part you are asked to determine the mam moment that can be applied to the beam if it is bent about the z axis. They then ask you to redo the question bending about the y axis. This is probably a really simple question but what is the...

Homework Statement A uniform rod AB of length 4m and mass 2kg is suspended in a horizontal position by two vertical strings attached at points p and Q where AP=1m and AQ=3m. When a particle of mass 3kg is attached at point R of the rod, the rod is on the point of turning about point P...

Homework Statement Fixed end beam with Length = 1m Load 1 = 58.86n @ 0.4m from A Load 2 = 39.24n @ 0.85m from A Find Ma, Mb, Ra, Rb Homework Equations Not Sure, where help is needed The Attempt at a Solution Well i think, almost sure from 2 methods that Ra = 40.52511...

Homework Statement A bicycle racer is going downhill at 11.0 m/s when, to his horror, one of his 2.25 kg wheels comes off when he is 75.0 m above the foot of the hill. We can model the wheel as a thin-walled cylinder 85.0 cm in diameter and neglect the small mass of the spokes. How fast is...

Homework Statement r-bond length (in anströms) q-charge (in debyes) CO2 r(CO)=1.1867 q(C)=1.1352 q(O)=-0.5676 angle between them is 120 deg Homework Equations The Attempt at a Solution I know I have to make vectors and then add them, but I don't know how to make the vectors. I...

Homework Statement A flagpole of mass 25kg and 2.5m in length is held in a horizontal position by a cable shown in the diagram. The centre of gravity of the flagpole is at a distance of 1.5m from the fixed end. Determine: a the tension T in the cable; b the vertical component of the force...

3D Equilibrium(and Moments) Homework Statement Homework Equations Sum of the forces in x=0 Sum of the forces in y=0 Sum of the forces in z=0 Sum of Moments (at a point) =0 (of x,y,z) The Attempt at a Solution Since it is a fixed end there is 6 unknowns right at the origin (Ax, Ay, Az...

I am wondering if there is a source of the magniude of the Dipole moments of all the planets and the sun, m. m(earth) is 8*10^22 A*m^2. The Magnetic Field and the Electric Field such that: Br = Mu0/4/pi*2*m*cos(Theta)/r^3 Btheta = Mu0/4/pi*m*sin(Theta)/r^3 Mphi = 0 Er =...

Homework Statement The direction cosines of the force F are cos \varthetax= .818, cos\varthetay= .182, cos\varthetaz= -.545. The support of the beam at O will fail if the magnitude of the moment of F about O exceeds 100 kN-m. Determine the magnitude of the largest force F that can safely be...

Homework Statement Here is the problem I am stuck on, need some advice Homework Equations ----- The Attempt at a Solution I found the moment to be -19.282 for the system shown (not sure if it correct) but I am confused about how to drawing will look for the equivalent system. (- is added for...

Just figured I'd throw this up here. I was able to solve for the reaction at E when a=2 but when I tried for a=7.5, I wound up with something completely different. I was wondering what I'm not incorporating into the steps to solving this. Also, it says determine the reactions at A and E. The...

Homework Statement Derive the moments equations for a plasma. I specifically need help developing the 2nd moment equation (the Energy Balance). I can't get one of the terms... Homework Equations The Boltzmann Equation: \frac{\partial f_{\sigma}}{\partial t} + \vec{v}\cdot \nabla...

I have a couple problems that I can't seem to get. The first I'm really close, I can tell, because my professor did one that was similar in class. The answer the book gives is 250 lbs, I'm coming up with 225. The second I think is similar to another problem he did in class but I'm not...

Hey guys, I need some help. I have an old fortran program that needs axial moment of inertia as well as polar moment of inertia. I have the part in Unigraphics NX5.0, where I can get the mass, volume, radius of gyration, and moment of inertias about each axis. However, I cannot find where to...

Hi, I'm currently working on an imaging problem that oddly requires some physics. Basically, I'm given a set of gray scale pixels and I have to determine whether they're a fiber or just random noise. My question is, how do I calculate the moment of inertia of the pixels while considering...

Homework Statement A system of spin 1/2 magnet moments with μ = 1*10^-23 Am² are in a magnetic field of 0.2T. At what temperature will 90% of the magnets be aligned parallel to B? The Attempt at a Solution I think I have found the relevant equation: U=-μB(N↑ - N↓) where U is the...

Homework Statement Let Y1, Y2, ... Yn be a random sample from the distribution with pdf \frac{\Gamma(2 \theta)}{[\Gamma(\theta)]^2} (y^{\theta -1)(1-y)^{\theta -1} for 0 \leq y \leq 1 I have to find the MME for theta Homework Equations This is a beta distribution where m = n =...

Hi sorry I am rather new to all this but I was woundering if I could get some help? Im currently studdying for my Uni's resits over the summer which fall in just a few weeks time. Iv started to go through some of the old past pappers and I've got stuck on the same bit over and over again...

Im having problems with two questions, the first is linear acceleration, A 6.00-kg cylindrical reel with a radius of 0.600 m and a frictionless axle, starts from rest and speeds up uniformly as a 4.00-kg bucket falls into a well, making a light rope unwind from the reel. The bucket starts from...

Homework Statement I'm not sure how to go about finding the following moments: M_{x}= \int \int\ y dx dy M_{y}= \int \int\ x dx dy Where the region is bounded by the ellipse: \frac{(x-2)^2}{16}} + \frac{(y-4)^2}{36}} = 1 Homework Equations Listed above... The Attempt...

Hi there... I'm not sure how to go about finding the following moments: M_{x}= \int \int\ y dx dy M_{y}= \int \int\ x dx dy Where the region is bounded by the ellipse: \frac{(x-2)^2}{16}} + \frac{(y-4)^2}{36}} = 1 I tried this several ways. I drew the ellipse and found the bounds to be -2...

We can easily write down configuration of electrons in an atom of given element. The question is how can I calculate the magnetic moment of given atom knowing configuration of electrons in that atom? Or maybe some other data is needed? Especially I am interested in calculation of magnetic moment...

Moments of Inertia, Centres of Mass... help please! Homework Statement A rod of length l rotates about an axis that runs perpendicularly to the rod through one end. The linear density p(x) of the rod in terms of the distance x from the axis is given by: p(x) = p0(1 + (x^2/l^2)) where...

Homework Statement http://img376.imageshack.us/img376/1033/questionii7.jpg The diagram shows a cross-section ABCD of a uniform rectangular block of weight W. The lengths of AB and BC are 2a and a respectively. The edge through A rests against a smooth vertical wall and the edge through B...

not totally sure this should be in the advanced physics section. its a general test your knowledge question of everything youve learnt, so naturally i can't remember anything... a magnet of magnetic moment U is droped such that it falls down metal tube of length L. the magnet's magnetic...

If a something is rotating about an axis with a constant velocity is the sum of the acting moments 0 since no acceleration is occurring? Moment = mass x acceleration x distance If acceleration is 0, the moment is 0. Is this correct?

can someone help me with this problem? E[(x^3 + 7x^2)^3] what is the central moments? mij=E[(x-xbar)^i * (y-ybar)^j]

Hi I have a few problems from 'Physics for Scientists and Engineers' by Serwat and Jewett, chap 10 Prob. 51 A cylinder of mass 10 kg rolls without slipping on a horizontal surface. At the instant its centre of mass has a speed of 10 m/s. Determine (a) the translational kinetic energy of...

Homework Statement At a particular stage of the manufacturing process, a robotic arm has the position and loading shown in the figure; http://img246.imageshack.us/img246/5498/25481552jo0.th.png Calculate the direct stresses due to bending and the shear stresses due to torsion...

Simple moments ! Can't do ! Urgent Homework Statement Determine the reactions at the smooth collar A, the rocker B and the shortlink CD. Homework Equations RC = Normal reaction at smooth collar A. RN = Normal reaction at rocker B. RD = Normal reaction at D. Moment at rocker B is...

Homework Statement A yo-yo consists of two uniform heavy discs, each of mass M and radius R, connected by a light axle of radius a around which one end of a string is wound. One end of the string is attached to the axle and the other to a fixed point P. The yo-yo is held with its centre of mass...

A uniform Disk of radius 0.18 m is mounted on a frictionless, horizontal axis. A light cord wrapped around the disk supports a 0.57 kg object. When released from rest, the object falls with a downward acceleration of 2.6 m/s^2 What is the Moment of Inertia of the disk...

Homework Statement A non-uniform plank of wood AB has length 6m and mass 90kg. The plank is smoothly supported at its two ends A and B, with A and B at the same horizontal level. A woman of mass 60kg stands on the plank at the point C, where AC=2m. The plank is in equilibrium and the...