# Questions tagged [moments]

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### Self Locking Brake Question

I've been staring at this problem for statics for quite a while now and I just don't understand it. The question states: "The brake is to be designed to be self locking, that is, it will not ...
9 views

### Justification for choice of beam stiffness at pinned far-end member

I’m reading off an example provided by the ICE structural analysis book, specifically example 4.7 (moment distribution method) I dont seem to understand why the stiffness from member D-C is 4EI/L ...
1 vote
97 views

### What is the moment of inertia of a circular segment?

Hi I read this response but it isn't exactly my situation I have a circle where the axis of rotation is on the c axis like this for a segment equal to the green. Specifically, I have a round steel ...
65 views

### How do I determine the moment of force that would have to be applied to the shaft to open the gate in this question on fluid statics?

I am presently studying fluid statics from Munson's textbook. I do not understand part (b) of example 2.6. The full question is as follows: GIVEN The 4-m-diameter circular gate of Fig. E2.6a is ...
28 views

### Period of oscilation of thin plate in the form of circular section

A thin plate of mass m in the form of a circular section of radius R and angle alpha is hanged to oscillate back and fort from a horizontal support. Find its period of oscillation. I am confused how ...
31 views

### Moment of a unimorph cantilever

I know as a general rule that the moment is the integral of stress multiplied by cross-sectional area (gives force) with the perpendicular distance from force, as mentioned in the lecture notes : Now,...
70 views

### Does a disk placed in a pipe perpendicular to flow direction of fluid feel dynamic pressure or total pressure?

There are two discs in the pipe but not at the same time. You can consider conditions with X but without Y, then with Y and without X. I am pretty sure that disc X will feel less force from fluid than ...
82 views

### What happens if we have a rotating shaft with high RPM but very little torque?

If there are heavy components mounted on it, what will happen? I think it accelerates very slowly, but reaches at the highest RPM at the end because torque is equal to angular acceleration * moment ...
52 views

### Deflection of a log splitter beam

I'm designing a machine that can be simplified as a log splitter. It will have a long, central beam that will resist both the forces of a force pushing out and the moment that will be caused by the ...
32 views

### Designing a footing to accommodate changing applied moment under ULS constraints

I am currently working on a system that will calculate the reaction distribution $p(x)$ across a footing with an applied load $P$ and applied moment $M$. There is one case that has me stumped: when ...
75 views

### What causes an EUC to propel forwards when leaned forwards?

I have heavily edited the question, as its previous standing was quite hopeless Thinking about a simple model of a unicycle, where the rider is a uniformly distributed rod and the unicycle just ...
1 vote
638 views

### 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 ...
117 views

### 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 ...
1 vote
623 views

### 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 $p$ ...
1 vote
101 views

### 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 ...
1 vote
145 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....
53 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 ...
165 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 ...
25 views

### 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. ...
3k views

### 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?
40 views

### 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 ...
97 views

### 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 ...
257 views

### 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 ...
2k 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 ...
802 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 $P$ ...
268 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 ...
1 vote
1k 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, ...
87 views

### 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.
1k 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 ...
76 views

### 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 ...
504 views

### 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 ...
1 vote
375 views

### 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
147 views

### 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 ...
40 views

### 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, ...
376 views

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
255 views

### 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 ...
1 vote
886 views

### 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 ...
95 views

### 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 ...
2k 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 ...
1 vote
166 views

### 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 ...
154 views

### 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 ...
60 views

### 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 ...
170 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)...
141 views

### 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 ...
2k views

### 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
39 views

### 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, ...
85 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 ...
3k 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? ...
1 vote