Questions tagged [statics]
Statics is branch of engineering concerned with the analysis of forces and moments on physical systems in static equilibrium.
228
questions
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2answers
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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?
12
votes
5answers
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How to calculate lever force when lever has uniformed distributed load?
We have a simple class 1 lever:
$$\begin {array}{c}
\text {5,000 kg} \\
\downarrow \, \downarrow \, \downarrow \, \downarrow \, \downarrow \, \downarrow \, \downarrow \, \downarrow \, \downarrow \, \...
12
votes
4answers
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How do I calculate the forces on a desk and its legs?
I have a design for a desk, and I'd like to not just guess at how strong it'll be, but I can't find an explanation on how to figure out all the forces involved that doesn't assume I already know a lot ...
10
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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 ...
10
votes
2answers
31k views
How to deal with a point force acting right on the hinge of a beam?
I have been attempting to solve a question where there is a point force acting on the hinge of a beam. Here is the problem:
I am not sure how to deal with the 2 kN point force at $C$ ($C$ and $E$ are ...
8
votes
2answers
88 views
Moment equation from dynamics differs with equations from physics & statics. Where did I go wrong?
In my dynamics class, we're being asked to solve the following problem:
My Attempt:
Since I'm given the initial velocity, final velocity, and distance, I solved for the acceleration of the plane ...
7
votes
3answers
884 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 ...
7
votes
1answer
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Calculate effort to raise hinged lever with distributed load
My father-in-law would like to install a hinged stair system in his garage that allows him comfortable access to his attic space.
He wants the stairs to swing up flush with the ceiling when not in ...
7
votes
1answer
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What is the benefit of additional planetary gears?
A planetary gear is a gear that rotates not around an axle but around another gear known as a sun gear, or star gear. I have designed prototype systems in the past that used a single planetary gear ...
7
votes
0answers
523 views
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 ...
6
votes
3answers
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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 ...
6
votes
5answers
334 views
Height limits of brick and mortar tower?
What are the factors limiting the height of a "tower" made of typical fired brick and mortar?
By "tower", I mean a structure whos point is to be tall, and can support a human standing on or near its ...
6
votes
1answer
435 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 ...
6
votes
1answer
442 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 ...
6
votes
1answer
469 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 ...
5
votes
3answers
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Does the length of a beam change upon deflection?
I have made a Python program in which I have computed the deflection of a beam.
I am plotting the deflected beam and am now asked to show the length of the beam.
If the beam is not deflected, it is ...
5
votes
4answers
4k views
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 ...
5
votes
1answer
178 views
How to draw a shear force diagram when two forces are acting at the same point
I am working on this question on my statics assignment:
Approximately at point B there are two forces, 20kN and 50kN.So far, I have only calculated global equilibrium and got the following values:
$...
5
votes
1answer
6k views
Shear Force Diagram of a Simply Supported Beam with triangular load distribution
I've been attempting this fundamental shear force diagram problem for several days, but can't seem to get the correct result. I'm trying to calculate the shear force diagram in terms of $x$, but I'm ...
4
votes
1answer
2k views
What is the advantage of statically indeterminate structures?
Most of the real life structures are statically indeterminate.
What is the benefit of designing a statically indeterminate structure instead of a statically determinate one?
I don't mean only beams ...
4
votes
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 ...
4
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3answers
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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?
4
votes
1answer
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What angle - for a strut - provides the greatest vertical strength/support for a cantilever?
I want to affix a cantilever to wall. I will support the other end of the cantilever with a strut made of wood, that attaches to some point on the wall below the cantilever, as shown in this sketch (...
4
votes
4answers
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How to calculate a tripod table's stability?
I have designed a circular, 800 mm (31.5") diameter tripod table. The top is made of stone and weighs 40 kg (88 lbs). The height of the table is 750 mm (29.5"). There is a central column with tripod ...
4
votes
2answers
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How to solve an overconstrained static free body diagram?
How does Force Effect https://forceeffect.autodesk.com do it? Given a 10m long bar angled as the hypotenuse of a 3, 4, 5 triangle with an xy pin constraint a (0,0), another xy constraint at (4,3), ...
4
votes
2answers
958 views
Statics and Structural Analysis: Determinacy in beams/frames
I have a question about the methods to decide whether a beam/frame is determinate or indeterminate. Typically you can count the number of reaction forces and compare them to the number of elements to ...
4
votes
1answer
149 views
3D construction [closed]
Can someone please tell you what to start with to construct a Kids Bike Trailer as 3D.
It should select material and geometry. I think I should start sketching with forces (children's weight) and ...
4
votes
2answers
5k views
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 ...
4
votes
1answer
83 views
Dimension of the unidirectional mechanical clutch
This is a problem from the book Engineering Mechanics Statics vol-1 by Meriam Kraige.
The elements of a unidirectional mechanical clutch are shown in the figure.A torque $M$ applied to the outer ring ...
4
votes
3answers
117 views
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 ...
4
votes
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 ...
4
votes
1answer
47 views
How to apply static failure criteria for bending stress in an angled cylindrical surface?
Let’s say I have an irregularly shaped bearing with a cross section that looks like the angled surface of a conical frustum, shown below.
If a bending moment is applied which causes the inside ...
4
votes
0answers
122 views
Calculating a pull force between two pieces of plastic
I have an HDPE pin, 2 mm high, 2 mm diameter, that I impress into a flat plaque of hot HDPE. It is not hot enough to melt the pin, but still hot enough that the material will shrink 4% in 24 hours.
...
3
votes
3answers
1k views
Why does the minimum force have to be parallel to the incline?
If we have an object on a frictionless inclined bench, why does the minimum force applied to keep it steady have to be parallel to the incline (or perpendicular to the reaction force)?
In other words,...
3
votes
2answers
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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}{...
3
votes
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 ...
3
votes
2answers
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Why is there a moment at the cross section end when you cut a body?
I just started mechanics of materials, and it seems that my knowledge from statics has gotten rusty over the summer. But there was a new concept introduced in the first example problem today.
There ...
3
votes
2answers
4k views
How to calculate the forces on members of a frame, due to a distributed pressure load?
I am trying to calculate the force sustained on the three labelled members of this frame (Members 1, 2 & 3). The frame will experience a uniform pressure of 1000 kPa in the area enclosed by the ...
3
votes
5answers
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Do flexible water hose cause pressure drop with constant flow?
My dad has a tub by a lake.
He has a water pump in the lake to pump up water into a tub.
He claims that if he use a flexible hose, the pressure in the hose at the top will be lower than if he use a ...
3
votes
2answers
804 views
How does the number of braces in a balsa wood tower affect the load capacity?
I am deciding between two design ideas for a project in which I have to build a balsa wood tower that can maximize load weight and minimize structural weight (maximize efficiency). I've included a ...
3
votes
1answer
673 views
Car which can climb the ramp of higher inclination
Two automobiles both of which have the mass center located midway between the front and rear axles,are identical except that one is front-wheel-drive and the other is rear-wheel-drive.The cars are ...
3
votes
2answers
40 views
Would friction forces impact a torque measurement transmitted through a gear box
I want to be able to detect very small torques placed on the end of a cantilever beam. These torques are very small - 1mg by 10cm. I am trying to make this on the cheap and use a load cell.
I plan ...
3
votes
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 ...
3
votes
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 ...
3
votes
1answer
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Is the Qmax of an T-Beam equal if calculated both above and below the neutral plane?
I was doing a question involving a T-Beam question wrong since I was selecting the wrong area to use for $Q_{max}$ when trying to maximise the shear stress.
$$\large{\tau}= \frac{VQ}{It}$$
A friend ...
3
votes
2answers
87 views
Derivation of the stiffness of a uniformly loaded cantilever beam
The stiffness of a uniformly loaded cantilever beam is given as follows:
I am trying to derive the stiffness, but I am facing a problem. I would be glad, if someone could help me out.
What I have ...
3
votes
1answer
564 views
How do I determine the reactions at the base of a tethered T-frame?
I received a tricky bonus question today in my engineering class:
I've begun by equating all moments and forces to zero, about an arbitrary point, which I labeled at $C$. Finally, I attempted to ...
3
votes
2answers
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 ...
3
votes
2answers
430 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 ...
3
votes
1answer
4k views
Drawing the shear and bending moment diagram of a 2D rigid frame [closed]
I am taking a civil engineering course that we are constantly asked to tackle questions that are not really covered in the course. I have been looking for suitable reference materials but with no ...
