Moments Definition and 598 Threads

Hey everyone. First time poster here. I was helping a friend do some Statics homework (I completed the course last Fall), and I ran into a really unsettling problem. I have done this problem over several times with the same result. When I do the problem only summing forces in the X and then Y...

Hello, Can anybody explain how the aerodynamic moment is calculated for an airfoil ? I was reading the first chapter in "Fundamentals of Aerodynamics" by Anderson & the formula for aerodynamic moment for the lower surface of the airfoil confused me. Is the aerodynamic moment calculated about...

I'm looking at a problem and am having trouble finding the force using moments. To be honest I'm not sure am i going about it the correct way. Attached is a sketch of the problem, Is the cclockwise moment about A = .5m(1000N) = 500Nm and the anti clockwise moment about A = .75m(F)...

Homework Statement Find the MGF and all the moments for X\sim N(0,1) 2. The attempt at a solution For the MGF, I have: M_X(s)=\displaystyle\int_{-\infty}^{\infty}e^{sx}\frac{e^{x^2/2}}{\sqrt{2\pi}}\,dx = \ldots=e^{s^2/2} Next I found that: M'_X(0)=E[X]=0 M''_X(0)=E[X^2]=1...

I have to find the moment generating function and find all the moments of $X\sim N(0,1)$ For the MGF, I have: $M_X(s)=\displaystyle\int_{-\infty}^{\infty}e^s\frac{e^{x^2/2}}{\sqrt{2\pi}}\,dx = \ldots=e^{s^2/2}$ Next I found that: $M'_X(0)=E[X]=0$ $M''_X(0)=E[X^2]=1$ $E[X^3]=0$ $E[X^4]=3$...

Homework Statement The handle of the hammer is subjected to the force of F = 20. Determine the moment of this force about the point A. http://s3.amazonaws.com/answer-board-image/3214a2db-1a55-4648-b582-5f36f0f34451.jpeg Homework Equations Principle of moments: Mo = FxY - FyX The...

Could someone take a look at what I am working on and tell me if I am on the right track? #1: Determine the moment of the 200 N force about point B. Please see attached picture for FBD. First I find the x and y components. x = 100N y= 173.2N, which are perpendicular and parallel to...

Homework Statement My questions are as follows: (1) If I apply a force (B) on a beam with a center of gravity at the middle(A), it will JUST cause a moment, correct? (2) If I remove this fixed point(A), and no gravity or any other forces are present, will it still JUST cause a moment or will...

Hi, I am sort of new to Physics forum but I am urgently in need of help. It would be very much appreciated if you could clear my confusion. Let me break them down into bullet points instead of one giant paragraph. 1.Dipole moments are vector quantities. I can just add them up like I do to...

Homework Statement A mass distribution in the positive x region of the xy-plane and in the shape of a semicircle of radius a, centred on the origin, has mass per unit area k. Find, using plane polar coordinates, its moments of inertia about the x and y axes. Homework Equations The...

A disc of mass 'm' rests on a rough horizontal plane. A light string that is wound onto the disc applies a horizontal force 'T' to the disc, which causes it to roll without slipping. a) Show that the acceleration from rest of the centre of the disc is = 4T/3m b) When T = mg, calculate...

Homework Statement Hi, I'm trying to complete my laboratory write up over my christmas break, and I'm struggling to understand how to do part of it. I emailed the lab demonstrator on December 9th, and the head of labs on the 18th and I've had no reply off either, so I'd really appreciate it...

I have no idea how to attempt this question, please help me. Anyone. The question : The diagram shows a wheel whose mass is 15kg and radius 1m being pulled by a horizontal force F against a step 0.4m high. What inital force is just sufficient to turn the wheel so that it will rise over the...

I have managed to rearrange an equation give to me to make I (moment of inertia) the subject. I am now having problems working out the values for parts of it. I = moment of inertia m = mass g = gravity h = height v = translational speed of the mass falling Tf = work done against...

Homework Statement Neglecting the size of the pulley at G, draw the shear and bending moment diagrams for beam AB. Homework Equations Fxnet=0 Fynet=0 Netmoment=0 The Attempt at a Solution\ What I want to do first is figure out the reactions at A and C, however I'm not sure...

Homework Statement The beam is subjected to two oppositve vertical forces and one horizontal force as shown. Determine the reactions at the supports A & C Homework Equations \sumforces in plane = 0 moment = force x perpendicular distance The Attempt at a Solution \sumY = 15 + RyC + RyA - 15...

For a Dirichlet variable, I know the means and covariances, that is, E[X_i] = \alpha_i/\alpha_0 Cov[X_i,X_j] = \frac{ \alpha_i (\alpha_0I[i=j] - \alpha_j)}{\alpha_0^2(\alpha_0 + 1)} But how can I prove these facts?

Hi people! Im having problems with my Prob.Theor. assignment=( I was hoping that u might be able to help me... I have 2 problems that i ve no idea how to solve!Oo Heres 1st one We re given rand. var. X, its mean value U, the stand deviation S (sigma). We need to show that E(z)=0 and...

Hello, run into a bit of a stumbling block studying moments perhaps someone could nudge me in the right direction. Homework Statement A uniform metre ruler is balanced horizontally on a knife edge at its 350mm mark, by placing a 3.0N weight on the rule at its 10mm mark. Calculate the weight...

Homework Statement draw/find the shear and bending moment diagrams of: Homework Equations V : shear M : bending moment ω : distributed load The Attempt at a Solution i already understood how the solution worked but i can't quite understand how the equations with the boxes were derived

Product moments of inertia-- what are they intuitively? Hi, I don't understand what the off-diagonal terms in the moment of inertia (tensor) matrix are intuitively...they are called the product moments of inertia...but if Ixx is the moment of inertia about the x axis, which axis is the Ixy...

When one finds the torque on a rectangular current loop one finds that it's equal to \vec m \times \vec B where m is the magnetic moment of the loop. I want to generalize this to arbirary current loops with constant current and I found that the torque would be equal to \left(I\oint...

1. A 200N ladder is being carried by two men. The ladder is 12m; one man standing at the end, and the other 2m from the other end. Find the forces exerted by each man, 2. Moment of force = Force * Perpendicular distance from force 3. Man at end; 6*200 Other man 2m from other end...

Homework Statement Consider the rigid beam below, which is loaded by five forces shown. The forces at A and B act to keep the total force on the bar equal to zero and the sum of the moments about point A equal to zero. a) Find the forces at A and B that satisfy the conditions stated above...

I came across a reference where there is a beam (lets say length L) both ends fixed... with a UDL of say "W" per unit length... i want to know how the end moments are W L^2/12 ...shudnt they be W L^2/4?? Its pretty simple mechanics. but it got me wondering,,,,

1) see pdf for question 2 I'm unsure how to calculate the force at the fulcrum since its not in equilibrium. I thought maybe i would add the two forces together, but that doesn't seem right. 2) so this question asks for what forces need to be applied at points A and B and i understand...

Homework Statement 1. 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...

Hi, I just wanted to know if I have answeedthis question correctly, if not where I have gone wrong. Thank you. [PLAIN]http://img148.imageshack.us/img148/6245/secondmomentofarea.jpg From what I have calculated, none are acceptable, but my calculations may be wrong

moment=rXF. I was wondering, in order to find r, you have to find a point on where the force is being applied right and subtract whatever you're revolving around from that point. My question is, can that point be any point only the direction of the force? Someone told me it has to be the...

Homework Statement Q: A beam has a solid square cross section of 100 mm and is simply supported by two supports 3 m apart. Calculate the dead load that can be safely supported when applied to the middle of the beam. * The question doesn't state material but I'm informed that it is mild steel...

Homework Statement Was doing some past papers in preparation for mock Cambridge exams when I ran into this question. Image should be on here I hope... Homework Equations Moment=Force x Perpendicular distance from pivot point? The Attempt at a Solution Dunno how to start this one...

Homework Statement The Hamilton-operator is given as \hat{H} and describes the movement of a free rigid object that has the moments of inertia I_{i} Under what circumstances is <\Psi|\hat{L_{1}}|\Psi> time-independent? Homework Equations...

Homework Statement Draw the axial force, shear force and bending moment diagrams. Show the locations and magnitude of the maximum and minimum values. Homework Equations See diagram. The Attempt at a Solution I've worked out the values from points A-B and then from points B-D. I...

Sometimes it can be instructive to make fun of yourself. What were your most memorable gullible moments? I can think of three: 1. In middle school a rumor went around that surplus WWII Harley Davidson motor cycles were available for $50. I spent weeks fantasizing about the customization I...

Homework Statement A uniform beam of weight 50N is 3.0m long and is supported on a pivot situated 1.0m from one end. When a load of weight W is hung from that end, the beam is in equilibrium. What is the value of W? I know that the sum of all moments about any given point on an object in...

I can seem to get the answer of 60N and 125mm from C Thank you for the help

"hanging accordian" balanced by opposing moments This is not a coursework problem, but it looks like one so I'm placing it here. If this is in error, do correct me. I'm a newbie :-) Assume an arrangement as below with a fixed surface, five ideal, weightless beams B_1 through B_5 joined by six...

Homework Statement Determine the principal moments of inertia of a circular cylinder with radius R and height h. Homework Equations Not sure. The Attempt at a Solution This is the first problem of this kind I attempt to solve. From what I've read on wikipedia, the tensor of...

How to get "Aha" moments in the middle of math exams? I find that when I work on math homework, I usually spend hours (or days) on a single problem, with little success. I usually go around in circles, and end up frustrated and clueless, with a huge mess of scribbled paper in front of me. Then...

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

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...

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

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?

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...

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...

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.

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...

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...

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...

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) +...