Questions tagged [statics]

Statics is branch of engineering concerned with the analysis of forces and moments on physical systems in static equilibrium.

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790 views

Why is the truss member between two fixed supports zero?

If i first assume the member(far left) to not be zero and use method of joint at both points of constraint, with both constraints having unknown vertical reaction, it cannot be solved. Load and ...
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7k views

How to find reaction forces in trusses?

I'm stucked at trying to find the vertical reaction at top and bottom constraint, i know how to do the rest. Can you show me how?
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cut section method in truss

For moment about D , how could the FGF sin26.6 generate moment about D ? FGF sin26.6 is located above point D , right ? How could FGF sin26.6 generate moment about D ?
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Draw the FBD of the entire frame, assuming that friction and the weights of the members are negligible. How many unknowns appear on this FBD?

Draw the FBD of the entire frame, assuming that friction and the weights of the members are negligible. How many unknowns appear on this FBD? This is what I've tried so far. I have four unknowns. ...
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2answers
623 views

Drawing conclusions about 3d truss from 2d model

I am on the task of analysing the load capacity of a warren-ish truss bridge similar to this one. I do not, however, have the software or skill to model and analyse a 3D structure. I was wondering ...
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3answers
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Finding downward force of lever bar

I am working on a DIY project, I am trying to replicate a bar compressor which for some reason is only sold in Europe so I thought it would be fun to make my own without having to waste so much ...
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1answer
59 views

Deformation of a fixed-fixed beam with perfectly plastic yield stresses

Here's the setup: The problem asks to find the relationship between the force $P$ and the displacement of B ($u_B$). I have done this correctly: $$P = \left(\dfrac{E_1A_1}{L_1}+\dfrac{E_2A_2}{L_2}\...
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2answers
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How does a pulley (with friction) satisfy equilibrium?

In the picture shown : Suppose that there is a man applying a force $F$ in order to support the box using a cord that wraps over a frictionless pulley (the system is in equilibrium and nothing is ...
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Why do we ignore horizontal reactions at roller supports?

When talking about roller supports in a statics problem, we say that the roller prevents only the vertical translation of the beam, but not the rotation or the horizontal translation of it. So there ...
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1answer
157 views

Equilibrium of a Rod with an Actuator

I'm an EE student by trade, but I've started a project that requires some mechanical analysis, and I've run up against a bit of a wall in my calculations. The system in question that I'm looking at ...
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2answers
204 views

Why does a simple pin-ended triangular (arched/curved) beam deflect more due to secondary effects (non-linear analysis)?

I cannot wrap my head around this. I have made two simple models, a triangular (or curved or arched) beam that is pin ended and has a single point load of 1N downwards at it's center, and a flat beam ...
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1answer
2k views

Calculating the moments due to reaction forces on a bent beam

I am trying to solve the following problem: EXAMPLE 2.10 Determine the reactions on the beam in Fig. 2–30a. Assume $B$ is a pin and the support at $B$ is a roller (smooth surface). ...
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3k views

How should I position two shelf supports for the best distribution of load?

I'd like to mount a shelf on the wall. I have two shelf supports to do so, like this: Relative to the shelf, where do I place the (blue) supports to achieve the best distribution of load?
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1answer
199 views

Why is the moment of forces on a rigid body in static equilibrium must be zero about any point, even if the position of that point is not on the body

Why is it necessary for the moment of the forces on a rigid body in static equilibrium to be zero about any point, even if the position of that point is not on the body itself.
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483 views

Truss problem with multiple unknowns

So ive got the moments of : B: Vertical : $\sin(75)AB + \sin(45)BC = 33\text{ lbs}$ Horizontal : $\cos(75)AB = DB + \cos(45)BC$ D: Vertical: $\sin(60)DC + \sin(65)DE = 100\text{ lbs}$ Horizontal: $...
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297 views

Free Body Diagram Problem

I'm having trouble with this problem: G and a are given, and we are asked to calculate A, B and C. What I've Done: The first thing I tried was a free body diagram cutting through A and C to create ...
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3answers
110 views

How can the linear relationship between curvature and bending moments be verified?

As part of an experiment, I'm verifying the existence of a linear relationship between curvature and bending moments for three beams using different materials. The plotted data can be seen below. ...
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1answer
436 views

Static equilibrium and moment

I hope I'm asking this in the right place. I have the following problem: and am to calculate A,B & C so that the system is in static equilibrium. I calculated A without too many problems. My ...
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1answer
385 views

How do we solve a rigid body indeterminate structure?

In statics we consider the force deflection constraints (i.e. assuming the structure to be flexible) to generate equations in order to solve the extra degrees of indeterminacy. So, basically if we ...
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1answer
2k views

How to calculate area of cross section needed to sustain a point load on a beam?

Consider a beam that is simply supported at both ends by fixed supports and a point load is applied directly in the middle. The force (F), length of beam (L), Young's Modulus (E) and tensile and ...
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1answer
5k views

Derivation if the formula for the surface moment of inertia of an isosceles triangle

For a isosceles triangle with base b and height h the surface moment of inertia around tbe z axis is $\frac{bh^3}{36}$ (considering that our coordinate system has z in the horizontal and y in the ...
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2answers
1k views

Given the tensile strength of a rod, how do you calculate the max weight that can be hung from it?

Given a 3.25" long, 0.125" diameter rubber rod with tensile strength 1200 psi supported on both ends, how much weight can you hung from the middle of it without breaking it? (This is not homework I am ...
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1answer
83 views

What kind of connection allows rotation at only one end?

We are looking to connect a non spinning coolant pipe to a spinning drill pipe. The connector needs to spin on the end with the drill pipe but be stationary on the end with the coolant pipe. Is there ...
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1answer
120 views

Statics - Volume of a Revolution [closed]

The given problem asks for the Volume of the given figure below You have a plane figure that somewhat forms a Two-circular base Paraboloid with radii 20 and 12 cms respectively, and an altitude of 16 ...
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1answer
314 views

What does the accuracy and precision values for a pipette mean?

Is the accuracy interval the tolerance for the instrument? Does the precision interval indicate a single standard deviation? And more importantly, does the precision assume a perfect operator (so the ...
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1answer
569 views

How/where to take moments to solve a static equilibrium equation

A 200×250 mm panel of mass 20 kg is supported by hinges along edge AB. Cable CDE is attached to the panel at C, passes over a small pulley at D, and supports a cylinder of mass m. Neglect the effect ...
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1answer
362 views

Simple statics vector analysis problem [closed]

I know the stack exchange does not help on hw problems, but please understand that I am just self learning these topics, I'm not in a class, and I'm using my dads old engineering mechanics book... Now ...
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1answer
205 views

Equilibrium of rigid bodies

I wanted to evaluate the safety of a walking aid device (walker). For example, if the way it is constructed and whenever I handle it, there are no risk of rotation, around its center of mass, turning ...
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3answers
3k views

Method of Calculating pressure of failure in a cylindrical container?

Is there a formula or method to calculate the pressure of failure of a cylindrical container of known material, thickness, and size?
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1answer
2k views

The boundary condition(s) for a continuous beam

I have a continuous beam across a center column (not sure whether I've draw it correctly or not) The Displacement and force diagram is as shown: The first diagram is the bending moment, second the ...
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1answer
14k views

How much weight can an aluminum tube beam support?

I'm building a set of monkey bars for my kids and want to use aluminum tubing (6061 T6) for the rungs. The tubes will be 3 feet long and 1 inch outside diameter. Supported on both ends with a circular ...
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3answers
14k views

Maximum Shear stress in Beams

I understand that for a rectangular c-s the shear stress distribution is parabolic and the max shear stress occurs at the neutral axis and has a value of 1.5V/A. Where V is the 'applied shear force' ...
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1answer
121 views

Finding the components of a vector along two other vectors

Using only the diagram above (Not using the questions in the diagram), i am asked to find the components of F2 along F1 and F3. I am having trouble with this question. I can easily resolve any of ...
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Mathematical representation of hinge and pin connection

Following on from this answer, I am reading about the difference between hinge and pin connections here, and I don't quite understand about it. I think I would need to see the mathematical ...
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1answer
1k views

Is pin column-beam joint always have less moment, more deflection compared to fixed joint?

I am referring to the answer here: It seems that on a simple structure (The diagrams on the left the images below have fully-fixed connections, while on the right the columns are pinned connections ...
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2answers
431 views

Does thickness impact resolving loads for an inclined beam?

I have a 3 m x 1 m x 1 m cuboid weighing approximately 10,000 kg. I am trying to resolve the vertical forces that will support the cuboid if the cuboid must rest at a 45 degree angle. Which of the ...
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1answer
436 views

Fragmentation of a curved cantilever beam under compression

Suppose we have a curved beam of a rectangular cross-section $A$, Young's modulus $E$, and a constant radius of curvature $R$. We now expose the beam to a vertical point load of magnitude $P$ at its ...
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2answers
278 views

Replacing a straight rigid link by a curved rigid link

Suppose we have a horizontal rigid bar hinged at one end to the wall. An inclined straight link hinged at one end to the same wall, is pinned to the rigid bar at its center. A load P is acting at the ...
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2answers
1k views

Does an external force at a joint between two members act on one member or on both?

I am trying to find the internal forces in the member at point G in the following illustration: My answer is different from the solution in the textbook and I think it has to do with how I'm looking ...
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1answer
444 views

How can I translate a pressure boundary condition to a velocity boundary condition for incompressible, viscous flow?

I have been working with an old code for modeling incompressible, 2D viscous flow out of a tank to understand a chemical process. There isn't much documentation and I'm not a fluid dynamicist, so I ...
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0answers
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Incompressible 2D pressure-driven flow: for Navier-Stokes equations in nondimensional form, how should I express pressure boundary conditions?

*I have updated this question. I'm using two codes for modeling incompressible, two-dimensional flow out of a tank. My fluid dynamics experience is pretty basic; I'm using the codes to understand a ...
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2answers
3k views

Determine the moment of inertia of a filled circular sector

Does anyone know how to determine the moment of inertia of the filled circular sector shown below? Apparently I have to use $dA=r\ d\theta\ dr$, $y= r\sin(\theta)$ and end up getting $I_x=\frac{r^4}{...
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1answer
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Where did I go wrong conceptually when attempting to calculate the maximum force on a truss at a given joint?

In the problem statement below, the question states to find the maximum load $\vec{P}$ that the truss can support. My method of approach was: Draw a FBD for the entire structure. Generally I would ...
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1answer
470 views

Differential equation of the vertical displacement of a cable

Given a cable (totally flexible) fixed at both ends, subjected to a vertical force $f(x)$ in his plane, with variable area $A(x)$, and variable elasticity $E(x)$ I want to find the differential ...
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1answer
949 views

Maximum deflection of a beam with both ends fixed and distributed load

I'm designing a part, and I'm trying to figure out what distance a slot should be from the bottom of the part. For simplicity in analysis, I'm approximating the region between the bottom of the slot ...
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2answers
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Horizontal and vertical forces on supports

Calculate the horizontal and vertical components of the reactions at the supports. I found the horizontal force for the pin by adding the forces to 0 and I know I can find the vertical reaction of ...
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1answer
189 views

Reduction of a simple distributed loading (correct question)

I am not yet at the chapter of equations of equilibrium, plus it says the couple moment is not 0, so I assume it just about the loadings and not including the reactive forces and reactive moment. So ...
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1answer
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Reduction of a simple distributed loading

This is the question, but with me 6 kN/m is 4 kN/m and 2 kN/m is 2.5 kN/m. And the length is not 4 but 9 metres. I am not yet at the chapter of equations of equilibrium, plus it says the couple ...
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2answers
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Determining the magnitude and coordinate angles of a resultant couple

Here is the exercise that I just can't seem to figure out. The answer should be 71.9 Nm with coordinate angles 44.2, 131 and 103. I know that the couple moments caused by the forces $F_1$, $F_2$, and ...
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3answers
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Why do we assume the moment is zero when analyzing a simply supported beam?

When calculating the reactions of a simply supported beam under any type of loading we assume that the moment about the reaction points is zero. What if our assumption is wrong and in actual practice ...