Questions tagged [moments]

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What causes an EUC to propel forwards when leaned forwards?

If this question belongs to physics stack exchange, please let me know and I will transfer it as soon as I can. Please also let me know if a diagram is neccessary of the model (I have not made digital ...
1 vote
1 answer
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Is the maximum bending moment of a fixed end beam always at end?

Mathematically, we can see that with downward loads only (only upward loads at the ends), the maximum bending moment for a fixed end beam of span $L$ either occurs at $x=0$, $x=L$, or where the shear ...
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How does a single point load cell eliminate the inluence of moment/load placement

All descriptions I have been able to find mention some variation of "due to their geometrical design single point load cells are immune to load placement" with no explanation on how is it ...
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1 answer
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Calculate compressive stress in shaft/key surface from torque

When designing shaft keys we calculate compressive stress in hub/shaft/key and compare it with allowable stress. The usual formula is $$p = \cfrac{F}{A} = \cfrac{\cfrac{M}{R}}{L_e \cdot t}$$ where $p$ ...
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2 answers
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Why is there a negative sign in case of moments caused by longitudinal stresses?

I came across the following relations in the plate theory. I, however, don’t understand the reason for the negative signs in Mx and My. There is, however, no negative sign in Mxy. I am guessing, this ...
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2 answers
133 views

Horizontal "pinching" force of an arch with applied moment

I have some Shape Memory Alloy wire programmed to curl from a straight beam into a circle. The force this generates is approximated as a uniform distributed bending moment along the length of the wire....
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2 answers
48 views

Max bending moment estimate

Context: I study aerodynamics and want to design and build an RC wing to put the theory I learned into practice. The essence of the theory I learned is: Given some mass of wing building material, how ...
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1 answer
90 views

Torque calculation for DIY friction wheel drive electric unicycle

I’m building a friction wheel drive electric Unicycle. Something like this; My question is how much torque should the friction wheel drive motor have considering the total mass of unicycle including ...
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Are you able to compute the bending moment exerted on the inner edges of parallelepiped box under inner pressure?

Suppose you have a parallelepiped box of dimensions $a\times b\times L$ with $L\gg (a+b)$, filled with simple distilled water exerting a uniform and constant inner pressure $p$ as reported in figure. ...
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2 answers
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What is the difference between mass moment of inertia and area moment of inertia? And why mass moment of inertia alone used for kinetic rotation?

What is the difference between mass moment of inertia and area moment of inertia and why mass moment of inertia alone used for kinetic rotation? Is there a possibility to use them interchangeably?
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Moment of a force

How come when I try using the formula M = rF (sintheta) I get Moment at D = .223 * 300 * sin(25)= 28.4 Nm but it's wrong. The answer uses cross product but I thought I could just use the magnitudes ...
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Is there a way to solve this complex statics problem algebraically?

This problem can be solve in 2 ways either I solve it with vectors which would be relatively painful and more time consuming and the other faster way is algebraically but I faced a problem when trying ...
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2 answers
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Torque for servos of tiltrotors

I am sourcing a servo for a tiltrotor drone and need to calculate the required torque to rotate the propeller and the motor from facing the front to facing the top. I understand that the minimum ...
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3 answers
895 views

How to calculate the moment of inertia of a propeller

I am trying to design a VTOL system that uses a servo to rotate a propeller and the attached motor so that it can provide thrust when it is at 0 degree and lift when it is at 90 degree. However, I ...
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2 answers
257 views

Understand how to choose the pivot point to calculate the moment of forces in dynamics

In statics, the net force and the net torque must be both zero. The net torque is the vector sum of all the involved torques (first moment of each force) about any arbitrary point $P$. The point $P$ ...
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4 answers
141 views

How do you simplify this load diagram?

Very rough sketch but I'm having trouble with a Shear and Bending Moment problem, and I'm pretty new to the topic. This is the original diagram: I already simplified the left side (not sure if it's ...
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3 answers
491 views

Which force generates the reaction moment in a fixed support

The question is: Which force causes the reaction moment at a fixed joint ? Lets consider a very simple example, a beam with one end connected by a fixed support to a wall. I understand that at A, ...
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2 answers
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Calculation of torque at the base

Hope you all are doing good. Can anyone please guide me on how to calculate the different torques at the base as shown in the image? Thank you for your time and help.
2 votes
4 answers
884 views

Is bending moment along a beam independent of the cross sectional area of the beam?

We know this that if the a cantilever beam (of any cross section) is fixed at one end and a transverse force is applied on the other, then it will bend. However, we just casually assume that the ...
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2 answers
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What will be the force F for the given brake system?

I am getting two ways to find F. One is Fx0.2=30 Nm which gives F=150N Other is Fx0.2-640x0.13=0 which gives F=416N I am confused which one is incorrect. I know problem is too basic but still not ...
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3 answers
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Find the maximum stress at a point in a machine member

A machine member having a diameter of 50 mm and a length of 250 mm is supported at one end as a cantilever subjected to different forces as shown in the figure. Find the maximum stress at points A and ...
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3 answers
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Does the turboprop engine torque get transferred to the engine mount and ultimately aircraft when engine is active?

When the turboprop engine is active, the propeller shaft rotates and causes the propeller to rotate as well, which in turn generates thrust. The propeller shaft rotates because of the torque (or ...
1 vote
1 answer
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How to find the reaction at the pinned support A as shown in the picture? [closed]

Please help me solve the problem. I need to know the reactions at A for both the cases as shown. Please note that E is a roller, D is a pin support , B is an internal hinge and A for case 2 is a fixed ...
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Lumber dimensions for machinery ramp

I would love help if anyone is able to offer any. I need to make a ramp to move equipment down a 3.5’ retaining wall. The ramp is to be 12’ long. I was going to use two 6” x 6” beams of Douglas fir, ...
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3 votes
2 answers
216 views

Parallel beam load cells, force transfer and maximum load

I'm going to experiment with a parallel beam load cell like this one: https://cdn.sparkfun.com/datasheets/Sensors/ForceFlex/TAL220M4M5Update.pdf. I've read somewhere that for a setup shown on this ...
1 vote
0 answers
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Unusual bending moment at simply supported beam in etabs [closed]

The horizontal beam is simply supported. I have assigned pinned to released the moment at the both ends. However, there's moment spike near the end in ETABS, what's the problem ? I have checked thru ...
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1 vote
1 answer
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What is the difference between a sum of moments about a point versus the moment at a point?

In class we're learning about moments, and I'm not entirely sure what is the difference between using an equation of equilibrium for the moments about a point (in this case C), and the actual moment ...
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1 answer
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How do I draw moments on hinged gates?

Hello I had a quick question regarding moments on hinged gates on submerged curves. Is there a general rule that we follow when we draw moments on hinges, do we draw the hinges in the direction the ...
2 votes
2 answers
987 views

How do you calculate the shear force on the screws that connect a door to a jamb via hinges

I'm trying to calculate the shear forces on hinge screws or bolts. Here is a schematic of the door with the relevant values: First, I took a free body diagram of the door and its hinges. The ...
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1 vote
1 answer
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How does the diameter of a worm gear affect the amount of force needed to turn it

Can anyone help inform a discussion I'm having with fellow modellers on a model railway forum? I have a locomotive powered by an electric motor turning a 20mm diameter worm gear meshing with a spur ...
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Machine Analysis Problem: Finding the vertical force at joint K

Help me in determining the right solution in this problem. I already have an initial solution here but when I compute, my answer does not match to the answer key. I would like to know where did I ...
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1 answer
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Diagrams of forces and moments of a statically determinate structure

I'm having difficulties with calculating the distribution of forces and moments in a statically determinate structure shown below. I'm especially confused about the arc part. Will there be only ...
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3 answers
101 views

BMD of the beam joined at intersection

4 beams are supported by the column at one side, another side is jointed together at the intersection. I have assigned UDL of 20 kN/m on all the beams. 2 beams are longer (3m), 2 beams are shorter (2m)...
2 votes
1 answer
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Rubik cube torque experiment - Correct equations and experiment set up?

Background I am attempting to experimentally find out the average torque required to rotate a single face of a Rubik cube. Little to no data is available as it varies from cube to cube. Some people ...
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3 answers
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How to derive fixed end moment of a beam fixed at both ends with a point force not in the center

So this is as far as I have gotten. The formulas written in green are the formulas that I have to find/ derive but I am hitting a wall. I know I am supposed to integrate but I am not sure where to go ...
1 vote
0 answers
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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, ...
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1 answer
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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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2 answers
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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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1 vote
1 answer
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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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3 answers
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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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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 ...
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1 answer
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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 vote
2 answers
231 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 vote
5 answers
154 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?
1 vote
3 answers
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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 ...
3 votes
0 answers
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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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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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2 answers
283 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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2 answers
395 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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2 answers
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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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