Questions tagged [moments]
The moments tag has no usage guidance.
62
questions
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Does anybody know where this calculation for the mass moment of inertia for an eighth of a circle comes from?
These attached photos describe flaps which are a portion of a circle and equations are attached as the mass moment of inertia, but there are no descriptions. I am using this for part of my research, ...
0
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1answer
20 views
Moment placed off-centre on a rotating body
Imagine a body which is allowed to rotated around its centre of gravity. I place a rotating moment, $M_d$ on a point which is a distance d from the body's centre. $M_d$ is only required to put the ...
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2answers
43 views
Torque required to start rotating a wheel about its center
Assuming i have a circular disc of a significant mass and diameter. Neglecting friction, if a motor is put at its center how do i calculate the torque required for the wheel to just start to rotate?
...
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1answer
37 views
How to calculate torque required to rotate assembly about the center
The image is a hollow cylinder: 2in OD, 1.76in ID. Connected is an angled bracket, 45 deg, that weighs 3lbs. The top rectangle piece connected to the bracket is 10 lbs,the dimensions are 31.1in x 14....
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3answers
84 views
Given 3 force measurements, what are estimated forces at other locations?
Given three unequal force measurements spaced equally 120 degrees apart on a circular plate at F_R, F_C, F_L, I need to calculate what the estimated force measurements would be if taken at positions ...
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0answers
11 views
Can we collide two Nano Spacecraft moving at 20% speed of light?
Nano spacecrafts are gram level silicon chips that will be accelerated to 20% of the speed of light to reach Alpha Centauri in 20 years.
I wonder if we can break the weight limitation by shooting ...
0
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1answer
43 views
Question in finding the direction of forces in a truss
This question primarily involves finding the direction of forces in a truss.
Let's give a scenario in Method of Joints
One source I found says that in finding the direction of the source, it would be ...
1
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1answer
24 views
How to determine the fixed end moment?
I was trying to compute the fixed end moment for the beam (given below) using equilibrium equation for x, y displacement and moment but there are 4 unknown variables reaction and moment at both ends ...
1
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4answers
74 views
If an aircraft's wing blows air downwards, how is the momentum conserved in level flight?
An aircraft's wing generates force of lift by directing the oncoming airflow down. How is this momentum balanced when the aircraft is not climbing, but maintains level flight?
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3answers
106 views
Statically determinate structure by adding moment
I'm considering the problem below.
It's a setup with a roller joint and a pinned joint with a hinge between the two rigid links.
Since there are now 3 unknowns for 3 equations and a zero moment at the ...
2
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0answers
30 views
Optimization: Most efficient way for multiple people to move boxes
We are moving house in a few weeks and have a couple of people helping moving the boxes. My previous experience from moving is of queues building up in small hallways and people getting tired from ...
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0answers
47 views
External moment over an hinge
I want to find the moments around points A and B in the following figure.
Suppose the structure is fixed at the point where $F_{ax}$ and $F_{ay}$ are located.
I consider A and B to be hinges so that ...
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2answers
64 views
How can I find deflection in a member that doesn't have a constant area moment of inertia?
I'm trying to calculate the maximum deflection in a simply supported member with a uniformly distributed load. The trouble is this member does not have a constant area moment of inertia. I've drawn a ...
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2answers
112 views
Maximum induced bending stress within the beam
The Maximum induced bending stress within the beam.
Given that:
$$\frac{My}{I}$$
The beam depth is 300mm, the width is 150mm. The beam is an I section beam with a 5mm wall thickness.
My ...
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2answers
33 views
How to determine the new position of a support if the beam is shortened (moments question)?
I am having trouble with this moments question:
A force F balances a 6m long, 100kg uniform beam at A. The beam will be shortened in length by 2.5m at B. Determine the new position of support A that ...
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0answers
42 views
Finding transformation of forces and moments
I have two sets of forces and moments, measured by two 6 DOF force/torque sensors at position A and B on a robot arm (B at end effector). My goal is to use this measurements to relate the forces/...
0
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1answer
111 views
Calculate deflection of a beam with an arbitrary shape
I have a beam with rectangular cross section, but rather an strange shape in the length wise direction as seen below:
So I have taken out the symmetry part of it:
And it actually has some nice ...
0
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2answers
74 views
Resultant force coordinate for parallel 3d forces acting on a slab
Apologies if I have done something wrong, first time posting on a stack exchange website.
Four forces act perpendicular to the surface of a circular slab (assume mass of slab is 0 and middle of slab ...
0
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1answer
44 views
Are there different moments of inertia for shapes and bodies?
I'm confused by this. There is a moment of inertia for a shape, let's say circle:
But if you make it 3D, you have a new moment of inertia:
Is there any connection between these two?
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1answer
625 views
Problem while solving for the moment of a cantilever beam
As in the first image,
Moment at any point between C and B should be 0.
But when I try to solve it by substituting equal and opposite forces at end C so that anti-clockwise moment of $F(l-a)$ and ...
2
votes
1answer
77 views
Why is the bending moment equation for a uniformly distributed load (w) across a length x on a structure given by w(x)(x/2)?
So for any structure, simply supported beam, three hinge frame, cantilever etc. where there is a uniformly distributed load. For example, for a simply supported beam with uniform load of w along the ...
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2answers
61 views
2nd Moment of Area of a ring
This is my first question here. I am having trouble finding the 2nd moment of area of a ring with a thickness 't' and radius 'r'. I seem to be a factor of 2 out.
What I do is I consider an area like ...
1
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3answers
96 views
Is there a 6th equilibrium equation for a static beam?
For a scholarship exam I'm taking, it takes simple enough ideas and then messes with them in crazy ways. In this question four of the equilibrium equations I'd use to solve this are linearly dependent....
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0answers
133 views
Finding Tension in cable in 3D Equilibrium
In a typical 3D Equilibrium problem.
Assume you have two cables points supporting a mass. The two cables are K distance above origin and form a quadratic triangle with the mass which is a the same ...
0
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2answers
273 views
Resolving moments and forces
The calculations for a design I am doing are making me go round in circles. I have simulated the design but I cannot seem to resolve this mathematically and it is really bugging me!
Below is an ...
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1answer
83 views
Is there a moment at a point between two connected sliders, when one is subjected to a force? (schematic shown)
Background: I'm designing a machine that uses an actuator to push an object. The connecting component may not take certain bending forces, therefore I'm trying to evaluate the system with a free body ...
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1answer
47 views
Sign convention-moment
I am having a hard time taking care of signs. Whether weāve made the cut at right or at left. Whether should we make the rotation according to axis x, y or z.
In this case, they assumed that P was ...
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2answers
2k views
The internal normal force, shear force and moment
How do I determine the internal normal force, shear force and moment at the point C?
$V_c = 0$, $N_c = 0$ and $M_c=3.75 kN/m$
I have already done this:
Where is the problem?
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2answers
2k views
Shear force and bending moment for continuous span
It's given that L1 = 5m, L2 and L3= 7.5m, w = 8.9kN/m , I am asked to find the bending moment using these coefficient.. Prior to this , i need to have the value of shear force first.Shear force = ...
3
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1answer
1k views
A way to calculate the magnitude of the moment
In my engineering textbook, I didnt understand the example given to explain the magnitude of the moment. It asks to calculate the magnitude of the moment about the base point O of the 600-N force in ...
2
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0answers
31 views
Most efficient way for finding the rotation angles after moment distribution (Cross method)?
First of all, I have taken a look at the Grinter's method, which is similar to Cross, but balancing angles instead of moments. My question assumes that we are using the Cross method, and not the ...
0
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1answer
81 views
How to solve for moment with uniform distributed load
How do we get the moment when there's a distributed load?
For example, the picture below has 9[(60)(18)]. I get that 60 is the distributed load and 18 is the total length of the load, my question is ...
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1answer
126 views
Shear force and bending diagram un-uniformly distributed load
I already got great help on this topic, but I'd like to make sure that I get it.
For example, take a beam of length 6 meters, left side fixed support and right side rolled support. There is a load of ...
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3answers
2k views
Transfering moment through internal hinge
My professor says, the internal hinge can not transfer moment:
But can we calculate $\Sigma M_A=0$ for whole beam ( without cutting it or something) this way?:
$\Sigma M_A=0 ===\Rightarrow M_A+(D_y ...
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0answers
19 views
Shift of joint in kinematically indeterminate system
Given ist the following system:
$$EI=100000\frac{\text{kN}}{\text{m}^2}$$
$$EA\to \infty$$
I'm suppossed to find the horizontal and vertical shift of joint g. My first approach was to use the ...
3
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1answer
131 views
Skewing of joints using virtual work
Given ist the following framework:
$$E=210 \frac{\text{kN}}{\text{mm}^2}$$
$$ EA \to \infty $$
$$ I_1 = 80000\text{cm}^4 $$
$$ \frac{I_1}{I_2} = \frac{3}{4} $$
$$ I_3=I_1 $$
Using the principle of ...
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3answers
943 views
Calculating moment of inertia for a hollow discontinuous circle?
This is a pretty simple problem, but I'm just not sure how to go about it. I want to find the moment of inertia of a discontinuous hollow circle. But since the shape is so irregular, I'm not sure how ...
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2answers
4k views
Transfer of moments in beams with internal hinges
We have a beam with 1 internal hinge just like the picture. We know the internal hinge can not transfer moments between AB and BD. We know the 30 kN force makes some moments on BD & AB. If B (...
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0answers
47 views
Pin, Slot, and Spring Equilibrium
I am checking to see if this is done correctly, the slot is a little confusing for me.
B is a pin in a slot, solve for the spring constant (k) so the 50 lb force applied does not move pin B
Solving ...
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3answers
2k views
is bending moment on roller supports at beams zero?
isn't the bending moment supposed to be zero on roller supports at beams?
then why isn't it zero here in this picture at x=2?
0
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3answers
817 views
Second Moment of Area for slanted triangle?
Consider this triangle with its centroid at $C$:
Then this is how I believe we can calculate the Second Moment of Area along the $x_{C}$ and $y_{C}$ axis:
$$\begin{align}
I_{xc} &= \frac{bh^3}{...
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1answer
87 views
Plastic Hinge by Skyciv
Is it possible to determine plastic hinge location of a frame in SkyCiv? Is it also possible determine moment -curvature relationship curve in SkyCiv? If yes, how?
2
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1answer
2k views
Sheet Metal Bending: stuck on calculating the minimum radius required
I'm used to calculate the minimum radius required for bending operations on both aluminum and steel sheets, given the following parameters: https://imgur.com/a/7akHC
Problem statement:
For a sheet ...
2
votes
4answers
280 views
Moment and Torque at a Single Point
As far as I know, moments/torques occur when forces applied are not in line. However, I often see moments/torques being applied at a single point in free body diagrams.
How can moment/torque be ...
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2answers
204 views
Finding the force in a cable of a rigid system
QUESTION (see attached image file):
I got stuck when trying to find tension for part A; see my working below.
and help me solve.
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1answer
2k views
Determine the reactions at A and C, knowing that Ī± = 30º [closed]
QUESTION(see image attached):
Really need help here can someone help me show how we get the solution as shown in the image file attached above.
okay since I was asked by one of the users ...
1
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1answer
498 views
Is radius of gyration same for both types of moment of inertia?
We know that moment of inertia is commonly known as second moment of area. Which is $\int_{}{} y^2 dA$.
However there another moment of inertia called as mass moment of inertia given by $\int_{}{} r^...
1
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1answer
667 views
polar moment of inertia for compound shape
I have a shape that I'd like to calculate the polar moment of inertia for:
the diameter is 600mm; the hexagon in the middle sides are 70mm each; the holes around the hexagon are 130mm from the center ...
1
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2answers
1k views
Maximum torsion shear stress in cylinder
I am trying to figure out am I doing this calculation correctly.
To get the maximum shear stress for a solid cylindrical pipe I need two formulas:
Moment of inertia = pi/2*r^4
Not sure what this ...
0
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2answers
86 views
moment of inertia forces and torque
I did some calculations to find out the moment of inertia and physical qualities of some metal.
I am using typical medium carbon steel.
I'll use a density of 7.8 g/m^3 until I get better numbers.
...
