Moment Definition and 1000 Threads

i am perplexed as to the first moment of area and second of area; i would like to know 1. why they come (how they are figured out and distinguished from each other) 2. what is meaning of these 2 moment of area in terms of physics what i have learned is that the first moment of area is used to...

Here is the diagram to the right. (a) Clearly, owing the fact that the bar is pinned at P, the net force on the bar is zero: ##\boxed{\Sigma \vec F = 0}##. The pin P applies an equal and opposite force to the one applied. This force keeps the bar from translating to a different position in...

First of all, sorry for the units. This is a problem I found on the internet and am confused about the solution. I calculated the two components of the moment (torque) to be ##T_x = 18\times Fcos(30)## and ##T_y=5\times Fsin(30)## The problem is, I got the proper answer (the two options...

Hello Physics Forums, I enjoy playing pool, my knowledge of physics is almost nonexistent, so I apologize in advance for my ignorance. In a nutshell, I would like to understand how the hardness of a pool tip effects energy transfer in that brief moment of impact when a pool cue tip hits the...

In defining the moment of a force about a point as "the tendency of one or more applied forces to rotate an object about an axis [going through a point, hence also about a point]", I see it logical to infer that it is somehow related to the angle between the force and the moment arm, but why put...

M = r x F r = 0 ∴ M = 0 But this is clearly wrong. For some reason, the "reaction moment" must exist. Why? Where does it come from? More specifically, which force(s) produces the bending moment, and at what distance(s)? Does it come from the reaction force form the wall on the left end of the...

Hello, I am a computer science major and Ex-Biology grad student, my knowledge in physics is humble, but I got a little curious when my professor derived the expressions of moment of inertia for different objects. The moment of Inertia of a thin disk is 1/2MR2, but it is the same as the moment...

Hi All I was wondering if there was a quick method of calculating the Second Moment Of Area about the Z axis shown below? I can quickly work out the Second Moment Of Area about the Y axis but the Z axis is proving very difficult and time consuming as the parallel axis therom needs to be...

My question is as follows. In the attached paper a formula is given on page 272 for the expectation of Tn (formula 23) and for the variance of Tn (formula 24). Now I would like to know what the formulas look like for Tn 's third and fourth central moment.

When I solved the problem using the conservation of angular momentum, I have got the correct result (ω = 0.006 rad/s). However, when I tried to find the answer using the conservation of energy the result was incorrect and I do not understand why.

Hello all I was wondering if anyone could figure out the what the equation below means, specifically the W term? The equation to calculate bending stress for a cross section that i have used and i know is correct is:- Bending Stress = Moment (M) * Distance From Neutral Axis (Z) / Second...

Hi all I was wondering if someone could help clear up some confusion about the Parallel Axis Theorem. I am trying to understand the purpose/benefit of applying the Parallel Axis Theorem with respect too the Second Moment Of Area. For example I have a beam that is under load. I have found its...

Hi all I was hoping someone could help shed some light clearing some doubt on 2nd Moment of Area. I know that if i had a beam that was loaded then the top of the beam would experience compressive forces. As i moved down towards the neutral axis these compressive forces would become zero. And...

Can someone guide me on how to approach this question? I tried to draw a quick diagram of what I think is happening here Does the question imply that this object is undergoing horizontal circular motion in the shape of a conical pendulum? Thanks for any help!

Here is the problem that I am finding difficult to answer I had tried using conservation of energy to do this question Where I know that the gravitational potential energy at the top of the slope equals to the sum of both the linear and rotational kinetic energy at the bottom of the slope...

I use the moment of inertia I = 1/12ml2 for an axis perpendicular and passing through the center of mass of a rod. In a cube built out of 12 rods I have 8 rods at a perpendicular distance l/2 from the axis through the midpoint of a cube. These 8 rods contribute the moment of inertia I1 =...

The equation that we saw in class is for a continuous charge distribution, I think that for this exercise I need to treat the system as a discrete charge distribution but I'm not sure. Also, I don't know how I can calculate the intensity of the electric field needed to move this charge.

Homework Statement: Derive the formula for the moment of inertia of a thin spherical shell using spherical coordinates and multiple integrals. Homework Equations: Moment of Intertia is (2MR^2)/3 I = (2MR^2)/3

Hello all! I have a mathematical question for you. I'm trying to design a thrust bearing that can withstand axial and moment loads. I've added a picture of a similar design. The design consists of two rings (grey) and sliding pads (blue) fixed on the bottom ring. The top ring slides over the...

Homework Statement: So i need to find equations to help me with a bifiler suspension experiment in which i will use a rectangular drop bar as the oscillating object, also any help with the method of this experiment would be greatly appreciated. The end goal is to find the moment of inertia...

I am reading about beams under distributed loading and shear stresses and needed to use the equation τ = VQ/It, where Q is the first moment of area. I understand that Q is zero about the neutral axis, and that this is, in fact, how the neutral axis is defined. The first moment of area above the...

I=(1/2)(6kg)(0.4^2 + 0.52^2) = 1.29 kg*m^2 initial: 34 mph= 15.2m/s 15.2m/s = (ω) (0.52m) ω= 29.2 rad/s after: 19 mph = 8.5m/s 8.5m/s = ω(0.52m) ω= 16.3 rad/s acceleration = (16.3 rad/s - 29.2 rad/s) / 5s= -2.58 rad/s^2 torque= |-2.58 rad/s^2 |(1.29 kg*m^2 ) = 3.3 N*m I am confused...

Hello, I tried to put it in an equation, but it didn't really work out. In this situation, the car was about the size of a model, and, while not exact, the radius of each wheel couldn't have been more than like a centimeter. Conversely, the ball was like twice the size of the car and had a...

So to start off, what I will do find the center of mass of each of the rods. So for the top rod, COM is at where y= 0.5 L and COM of the rod at the bottom is at x = 0.5 L. From there, how do I proceed in finding the moment of inertia using parallel axis theorem? Do I simply treat: ##I...

Hello to everyone. The question or debate here is how you obtain the commonly known equation of dipole electric moment: from the electrostatic potential equation for a multipole of order n: I understand it is related with Dirac delta functions but a step by step solution might be helpful.Thank...

https://www.physicsforums.com/attachments/250905 I know the answer, but am not certain how they got Lsin(angle) for R?

Hello everybody, Lets say we have an atom with an electron that have a spin. That spin can only pointing in 2 directions, in s_1=\hbar*1/2 and s_1=-\hbar*1/2 and therefore the magnetic moment of an electron is pointing on the opposite site. My Problem here is appearing when whe apply an...

Figure 1 shows the Turning Moment diagram of Single Cylinder four stroke Engine. Can anyone tell me, how the turning moment becomes positive at the end of suction and exhaust stroke. Net force F = Force due to gas pressure - Inertia Force - Reaction Force due to friction If the net force...

I've attempted this question, but the answer seems to be incorrect. Here's my workings: ##I=\int y^2 dm## - standard equation ##dM = \mu * dy * x## - take small slice and find mass of it ##x = 4y-16## - convert equation in terms of x to sub in later ##dM = \mu * dy * 4y-16## ##I=\int y^2 \mu *...

Homework Statement: Derive the formula for moment of inertia of a hollow sphere. Homework Equations: Required answer ##\frac{2MR^2}{3}## Consider a Hollow sphere. At an angle ##Θ## with the vertical, consider a circular ring whose moment of inertia is given by ##MR^2##. The most basic...

Hi all, I just wanted to get some clarification on 'resultant moment' when calculated in 2D for a beam which is fixed at one end (point A), and has a load applied at the opposite end (point B). My interpretation of 'resultant moment' would be calculated as sum(M) = Ma + FL, where Ma is the...

I have attached an Excel-worksheet in which the problem should be clearified. The problem concerns the calculation of the bending moment acting in a pin in double shear, experiencing a certain load from a hydraulic cylinder. The plate thicknesses should be taken into account. Specifications and...

I am having difficulties computing the magnetic moment for an even-odd (proton-neutron) nucleus. The formula is: $$\mu_J=g_J\times j\times \mu_N$$ I checked this helpful post...

The direction of x, y and a axes were shown in the highlighted part.. I think it is wrong. For red circled beam, i kinda agree that Moment about x-axis was defined as torsional moment.. While moment about z and y axes are bending moment... But for blue circled beam, I think that Moment about z...

Summary: Why is the electric dipole moment of the nucleus of an atom equal zero? Summary: Why is the electric dipole moment of the nucleus of an atom equal zero? I read about the hyperfine interactions that cause the altering of the energy levels of the nuclues of an atom. Under the...

The question doesn't specify whether we're talking about translation or rotational equilibrium, so I suppose it's both: In order for the body to have translational equilibrium: 60 N + F2 = 0 F2 = -60N However, in order to have rotational equilibrium: 60 N * 3m + F2 *8 m = 0 60 N * 3m - 60 N...

Hello As the angle of attack of an airfoil changes, the lift force ##L## changes both in magnitude and position (not in direction, always upward). The force location is a point called the center of pressure ##x_{cp}##. It is possible to transfer the force to any another different point along...

Hello! Can someone explain to me what is the anapole moment? I read several papers, and I understand its mathematical expression and its implications (parity violation for example), but I am not sure I understand physically what it is. For example I think of an electric dipole moment as 2...

Ratio of moment of inertia of a circle and that of a square having same area about their centroidal axis is: Sol: both area and square have same area: ##a^2 = \large\frac{π}{4}\normalsize d^{2}; \large\frac{d}{a} =\large \sqrt\frac{4}{p}## Ratio of moment of inertia of a circle and that of a...

I thought about solving it using components of IAB but since it is a scalar quantity it doesn't seems to be correct . I don't think Perpendicular Axis theorem will work as required Inertia is in the same plane.

Help me first understand the physical Universe that these twins live in. Has anybody ever measured physical matter from a different time frame other than the present moment? In other words, is there physical matter existing in a time other than the present moment? If there is no evidence of...

So there are two cases: a). free fall (straight forward for me) b). ladder rotating and jumping off in last moment (I am interested in trying to understand this case) I believe I should take into account momentum at the time the man hits the ground in both cases? The smaller, the better. Or...

Why a magnet bar would become aligned with the external magnetic field while a magnetic moment would precess around the external magnetic field?

While I am reading this article, it says moment of inertia is same at radius of ring and at the center of it. How is that possible?

My attempt-:I extended the axis and made a triangle by joining other adjacent vertex to the line such that its angles are 15°,75° and 90°.I found the distance between the centre of square and upper vertex of triangle by using law of sines.And then i found out inertia along upper vertex of...

A force of 1200N acts on a bracket as shown in the below figure. Find the moment of this Force about point A. Taking moments of components of 1200N force about point A. ∴ ##M_{A} = - (1200.Sin 30^{0} * 140) + (1200.Cos 30^{0} * 140)## ##M_{A} = 40.71 X 10^{3} Nm## I am confused, because...

I hope you guys can help me with this problem.. A top in the form of a flat, circular disc spins on a shaft that is inclined at an angle alpha to the vertical. Now I have to find the moment of inertia I for the disc about its centre on the shaft. My attempt was building I with spherical...