Questions tagged [statics]

Analysis of a system of bodies where all forces are in balance and there is no motion relative to a chosen reference frame.

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Mechanics behind Pringle Ring

Everyone knows about the famous Pringle Ring Challenge Does anyone know how I could develop a theoretical model to predict its stability?
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What curve does a rod form when bent to intersect 3 or more points?

Suppose that we have a sufficiently thin, flexible cylindrical rod of length $L$ made from a homogeneous, isotropic material, and that initially [at rest?] the central axis of the rod is a straight ...
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How do we account for the non-net accelerations for forces in static systems?

I've googled the heck out this (as a non-physicist) and found a ton of similar questions answered but did not find anything that made the light bulb go on. I don't think I'm a crank, so here it goes. ...
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Dropping vertices of an overdetermined statics system graph

In statics, the problem of determining the tensions of K cables that connect a structure made of N points and keep all points in static equilibrium implies $ND$ systems of equations, where $D$ is the ...
diffeomorphism's user avatar
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Obtaining point of application of Ground Reaction Force with use of a hyperstatic load-cell array platform

I'm looking for the theory of an experiment that is giving me a hard time to perform. I have an instrument composed of a rigid horizontal square plate rigidly supported under each corner by a load-...
heltonbiker's user avatar
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Is it possible for rigid objects to slip before friction is saturated everywhere?

A common technique in statics problems is to assume that static friction is saturated everywhere. Consider, for example, the following problem: A thin, uniform bar of mass $m$ lies on a uniform floor,...
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How weighing balance works and can balance itself?

i am new in this community and i was not able to answer in a similar post "how does a weighing balance that has 2 identical mass on both sides is capable of balancing after being tilted". i ...
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Pressure of rubber band on cylinder taking friction into account

Suppose I have stretched a rubber band around a cylinder of radius $R$ such that the rubber band is under tension $T$. My understanding is that in the ideal situation, with no friction, the band ...
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Static equilibrium question: Horizontal rod attached to a wall

I'm doing a problem on static equilibrium and I'm unclear whether a force exists or not. This is my force diagram: The setup is: a homogenous rod with a certain mass is attached to a vertical wall on ...
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Mechanics of Materials (pressure and temperature)

A solid right cylinder of rock core is surrounded by four rods made of mild steel (all-thread rods). The rods are placed equidistantly around the core in a square formation. The tops and bottoms of ...
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Derive the ideal shape for a dome and a cylindrical arch

A catenary is the ideal shape for an arch whose job is to support its own weight. First, would this be true for a surface of revolution about a vertical axis through the lowest point, i.e. would a ...
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What is the amount of force applied on my back while I'm brushing teeth leaning forward?

This is a question I've had for several years but never had the knowledge to calculate myself. Please keep in mind I don't have much background in physics (learned some on middle school I guess...), ...
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What is the physical explanation for $ cm(h_{min})= h_{min} $ when minimising the centre of mass of a can of coke?

There's an undergraduate statics problem that is about finding the lowest centre of mass of a coke can as it is emptied out (say through a weightless straw). The problem itself is not difficult and ...
capstain's user avatar
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3 answers
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Sign of distance/arm when finding moment/torque

I know that $M=Fd$, but when I have a negative moment, does the sign of the moment matter when I'm calculating for distance? If yes, then what would it mean when distance is negative?
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How do we pick the contact point for distributed contact forces?

Suppose I have two structures of three blocks of the same shape with mass 1.0. The structures are in the exact same poses. I have drawn two sets of forces that can satisfy static equilibrium. However,...
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Water Droplet on solid plate (Young's Equation via Force Analysis)

I was reading about Solid-Liquid-Air Interfaces pg 484 in Competitive Physics Volume 1 by Wang and Ricardo and we were proving Young's equation regarding the contact angle of the water droplet on this ...
Michael Li's user avatar
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Ladder against wall - reason for movement orthogonal source force?

Intro: I am under the impression movement is caused by a force, in particular without any boundaries a force causes an acceleration into the direction of the force. With boundaries, "the ...
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Inelastic static tetrahedron with 3 fixed vertices, and 1 free vertex with an applied force

This is a problem I've posed myself, which I cannot for the life of me figure out, despite it clearly having a definite answer. Given: A perfectly inelastic tetrahedron in three-dimensional space ...
Silas Hokanson's user avatar
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If two oppositely charged rods are placed near small pieces of paper why do they both attract the paper?

Take two oppositely charged rods, place them near small pieces of paper, and both rods will attract the paper. Why do both negatively and positively charged rods attract the paper in the same way?
rania khan's user avatar
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What is the correct intuition behind Varignon's Second Theorem? (See the example in the details.)

Consider, say, a rigid 2-D square sheet, of uniform mass density, initially occupying the square: $$-2 \leq x_1, \ \ x_2 \leq 2$$ in the $x_1 x_2$-plane. The plane is a frictionless table, on which ...
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Statics question: Free body diagram help for garage construction project

I'm building a climbing training apparatus in my garage that both rests on the ground and hangs by a rope from a hook attached to a ceiling joist. Here are some pictures of builds similar to what I'm ...
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Tension force transmitted to 4 attachment points

I have a given 3D vector of tension force ($\vec{T}$) and I want to find a way to transmit it through 4 strings that connect the attachment points $\vec{a}, \vec{b}, \vec{c}, \vec{d}$, whose values ...
Sergio García's user avatar
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1 answer
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Balance of an non-homogeneous object

Would a pencil balanced on its tip, remain balanced if the the tip was made of a material twice as heavy than the rest of the pencil?
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How do we decide which tension forces get included in the force- and torque-balance equations?

Consider a static equilibrium problem like the following: The uniform boom shown below weighs 700 N, and the object hanging from its right end weighs 400 N. The boom is supported by a light cable and ...
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Intuition behind First moment of area and link to centroids

I essentially have the same question, however only concerning the First moment, as this user ,however none of the answers satisfy my questions. I understand that we are trying to get a sense of the ...
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How to solve 3-variable planar vector equilibrium problems?

While it's quite straightforward to solve problems with multiple planar vectors in equilibrium for 2 variables, I'm having issues with those where I'm asked to minimize or maximize a variable along ...
Ariel Arévalo's user avatar
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Conservation of percent difference?

I was doing a lab to experimentally determine coefficients of static friction between two surface. This was the basic set up: The mass of the block is a known quantity. I was checking the maximum ...
Jean Valjean's user avatar
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Forces on bifolding door with horizontal hinge

I'm a programmer who's been put in charge of some motor control problems and I need your help, so please forgive me if the question is silly. The problem in question (see inserted picture) is ...
BasileSoftware's user avatar
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Counting experiment and standard error

I have a counting experiment: Let's say I have N identical bees. I take one of them, expose it to $\gamma$-radiation and look if it has died or survives. If it survives, I count it as 1 count. If it ...
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How to consider another Cartesian axis?

Well, I solved the problem. The point is that I used a x and y axis with x parallel to the inclination of the box, but I wanted to think differently, if one considers the y axis itself containing the ...
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Influence of couple-moment's position on bending moment diagram

The moment of two equally opposing force would create a couple-moment. Since the couple-moment value is invariant to the point considered to calculate the couple-moment, I can replace the two equally ...
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Transferable force

If I for example have two rectangular pieces of steel that are both W=40mm, L=1000mm, H= 40mm and are both completely ridged. One piece of steel is resting on top of the other piece of steel, if I ...
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When a force applies to a rigid body at point, then does every part of the body experience the same kind of force?

Suppose that a rigid body is static under the action of several forces that are applied at different part of the body. Then is it true that if one divides the body into small pieces, then each piece ...
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How does centre of gravity influence the equilibrium?

Ok! This really makes hard to think, how does a single point determine the object's equilibrium? If an object is displaced from its equilibrium-position & if the equilibrium is stable, the object ...
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How to approach a static analysis when objects are on differing inclines?

I think this sort of problem is known and relatively simple when on a single angle of incline, but I'm trying to understand a problem with two points of contact of a uniform vehicle where each contact ...
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How can the force acting at the fulcrum of a lever be calculated?

I know how to calculate the force applied to either or both ends of a lever system, but I would like to know how to calculate the force applied over the fulcrum of a lever.
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Stationary, static and strictly stationary/static?

Consider spacetimes which are asymptotically flat at null infinity. How to explicitly show that there exists a hyper-surface orthogonal killing vector field $k^{a}$ that is time-like everywhere in ...
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Can a body be in both static and dynamic equilibrium simultaneously?

I was just studying statics when I realized that a body can be in both static or dynamic equilibrium at the same time but I am not so sure. My textbook says that an object at rest is in static ...
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Calculate weight distribution on 2D plane

I am trying to figure out how I can have a formula for the weight distribution on a square. But let me just describe what I am doing, We have the classical horizontal beam support problem And I we can ...
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Intuitive understanding of the mechanism of uniform bending moment

So many explanations on uniform bending moment and I can't understand until now how it works. I can somehow visualise that in order to resist the external bending moments created by equal and opposite ...
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2 rods connected at a pivot and attached to a spring

I have a question concerning this problem First I calculate F1 by taking the origin at F2 and imposing equilibrium for the torque thus getting $ F_1 = \frac{a}{a+b} F $ and similarly for F2, then I ...
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How is a cupboard stable?

Take a cupboard or just a large wooden box. When pushed it a point above its center of mass, the cupboard topples because there is a net torque due to the friction and the force you apply. When pushed ...
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1 answer
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Applications for generalized Lami's theorem

Hello fellow physics enthusiasts! I recently came across with a generalization of Lami's theorem for four coplanar, concurrent and non-collinear forces in static equilibrium. I was wondering if anyone ...
Emmanuel José García's user avatar
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1 answer
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Minimum torque required to turn a large gear

I want to preface this by saying that this isn't homework, it's just a question I've made up myself (so it could just be impossible to solve), and I am a beginner so apologies if I miss something ...
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How to find Shear Force and Bending Moment in Finite Element Method for a cantilever beam with many elements

I have a cantilever beam with lots of elements. I am trying to find the sheer force and bending moment diagrams of the beam. EVERY SINGLE TUTORIAL AND EXAMPLE I SAW ONLINE SHOWS HOW TO DO IT FOR A ...
john wick's user avatar
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1 answer
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Confusion regarding calculation of amount of water in container to ensure lowest centre of mass

When I tried to calculate the volume of water that should fill a massed container such that the centre of mass of the system is the lowest, I obtained two separate results when two different methods ...
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How non-collinear forces balance each other?

In the system of parallel forces , all the forces are non-colinear. So how to they balance each other?. Here in this case a wooden plank is supported at its end by two supports. All the forces here ...
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2 answers
137 views

Torque equilibrium

It is a rather simple question from my assignment but I have a confusion that needs to be resolved. Find the mass $m$ that needs to be kept at one end of a thin rod of mass $M$ and length $L$, hinged ...
Rew's user avatar
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1 answer
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Moving an object from a height to the ground at constant velocity, difference between normal vs applied force

An object is at rest on top of a level surface such as a table at height $h$. Under this condition, a normal force is acting on the object from the surface of the table as well as the force of gravity....
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How come at a certain joint a truss is a zero force member and at another is isn't?

I have a slight confusion regarding zero force members. I'm analyzing a structure and I started at joint E and found that truss GE has a force of 8.4 [kN]. However, if I analyzed it at joint G, I can ...
Moriel Mankevich's user avatar