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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1answer
17 views

Deflection of L bracket [closed]

I want to calculate the deflection for an L bracket like https://imgur.com/a/0PabX0T to determine how thick I will need to make the steel for a workshop shelf. I have done the calculation using the ...
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Conceptual Question about Suspension Bridge Forces

Two walkways are suspended from vertical rods. In the first scenario, one long rod supports both walkways and is attached to the ceiling. In the second scenario, two shorter rods are attached to each ...
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Vectors as a function of theta [closed]

Express the vector $\vec{OA}$ and $\vec{AB}$ as a function av θ. Suppose that the angle between $\underline{OA}$ and $\underline{AB}$ is 90°. I have started to define the unit vector: $\underline{e}_{...
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How to solve for $T_1$ and $T_2$? [closed]

Hi all, I was wondering how to solve the question attached (see picture). It’s been a while since I did physics, and I was wondering if someone could take me step-by-step on how to solve it. I ...
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1answer
54 views

How can I calculate the coordinates of segments that form a hanging chain?

I'm trying to get a chain physics model with segments. I'm feeling rather stupid, but how can I calculate which is the new position of each dot when the chain moves its ends? expressed in another ...
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1answer
494 views

Eccentrically loaded bolts in which the plane of loading is parallel to the bolt plane

This are eccentrically loaded bolts in which the plane of loading is parallel to the bolt plane.When deriving an equation to this particular problem almost all books start by assuming that $$\frac{F_{...
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A problem about moment (torque ) [closed]

Everybody knows that moment of a force increases with distance. However, there is a problem about it that makes me confused these days: Let's take a look at this picture due to the formula M = F.d, ...
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How to derive the equation to calculate height of stopper? [closed]

I have a spherical ball of radius r places on an inclined plane of angle θ. What should be the minimum height of the stopper <...
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1answer
33 views

Physical meaning of internal bending moment

Here's the setup: The textbook, where this is from, first walks through how to find the strain and stress as a function of z, which is fairly straightforward. Then, it calculates the "total internal ...
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Moment of force about a point definition

In defining the moment of a force about a point as "the tendency of one or more applied forces to rotate an object about an axis [going through a point, hence also about a point]", I see it logical to ...
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4answers
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Static friction free body diagram on a flat plane

Do you include static friction on a free body diagram for a static box on a flat surface? Or do you just include Force of gravity and Normal force? We know when the box is moving there is Frictional ...
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Leaning ladder problem

Could anyone explain the case of a ladder leaning on a smooth floor and against a rough wall? It's not clear how there is a vertical frictional force at the wall despite having zero normal reaction ...
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Questions about potential energy and its corresponding force

The question arises when working at the following problem: A light wire is bent into a right angle and a heavy ball is attached to the bend. The wire is placed onto supports with height difference $...
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1answer
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Three hinged rods problem

This is an edited version (I added a solution and a physics concept related query) of a closed question that I'd like to see the answer to Three identical rods are connected by hinges to each other, ...
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Is static friction considered to be a conservative force? [closed]

The work done by static friction is 0.So shouldn't it be a conservative force?
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3answers
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How to calculate pressure/force on a triangle vertex? [closed]

Assuming those are identical triangles. We add some weights on the upper bar. The only difference is with the location of the weights and the size of the weights. Is there any difference on the ...
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Statics Question about Friction on an Incline

So for an object, say a block, on an incline, there hold three cases in which minimum force $P$ is dependent: a.) To start the block moving upwards.This is the case where static friction is at the ...
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571 views

Pressure of the same mass of fluids of different densities?

Suppose I have 2 fluids of different densities, and I pour the same mass of each fluid into 2 identical cups. I feel like I'm confusing myself here — on one hand hand, both cups contain the same mass ...
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Determining the magnitude of the projected component of the force problem [closed]

I can't figure out this homeworm problem. I know the answer is 147 N, but I don't know why. Determine the magnitude of the projected component of the force F = { 450 i - 250 j + 650 k } N acting ...
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1answer
247 views

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 ...
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2answers
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Varignon's theorem (Principle of moments) failure?

Varignon's theorem states that "If many coplanar forces are acting on a body, then the algebraic sum of torques of all the forces about a point in the plane of the forces is equal to the torque of ...
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1answer
189 views

Can someone prove the Principle of Moments from Newton's Laws?

Is it possible to rigorously proof the Principle of Moments from just Newton's three laws? Here's my formulation of the laws/axioms? Someone tell me politely if I'm wrong. Particles always follow ...
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1answer
42 views

Why is this force completely vertical?

I have the following system, which is in equilibrium: It's a bar that can pivot around A, and is held in place by a string at B I'm supposed to find the force applied to the bar at the pivot. I ...
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1answer
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Problem in statics in applications in engineering mechanics at coursera

in the first image the instructor neglected the reactions at point d and e while he was drawing an fbd to the whole structure ... Shouldn't we give attention to the reactions at d and e while we are ...
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2answers
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A question about the vertical part of the beam

I am solving beam type of problems finding reactions, moments...my question is how do I represent the F2 force that is acting on the vertical part of the beam (on the stick). Usually there is only a ...
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2answers
924 views

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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Why is the triangle the strongest shape? [closed]

I've been doing some research about buildings that sustain earthquakes and then it was mentioned that the triangle (or pyramid if we are talking about 3 dimensional space) is the strongest shape, why ...
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Can someone explain how does the -4222.50kN jump happen in the Shear Force Diagram of the beam [closed]

This the the problem https://beamguru.com/online/beam-calculator/?save=02461c5130daee73a8c73a51060e2adc Now I did the reaction forces correctly $R_a$ and $R_b$ and it matches with the ones the ...
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580 views

Best self-study books for static mechanics problems

Which book is the best for me to self-study/improve at static mechanics problems? I am looking for a book with a lot of ( only ) problems, not a theoretical book. Not only basic problems, the ideal ...
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How can one conclude upward force is related to tension in this question?

In preparation for the SAT Physics Subject Test, I have been doing extra practice problems. This one states: A garment bag hangs from a clothesline. The tension in the clothesline is $10 \,\text{N}$...
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Proof of the Law of the Lever

Is there an accepted proof of the Law of the Lever? I know of several attempted proofs, such as Archimedes's, but these either are incomplete or do not transfer to the setting of Newton's Laws. (It ...
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Find the center of mass of the body in the figure [closed]

In the figure below is a very simplified model the mass distribution of the human body shown, with head (mass 5 kg), Torso (28 kg), arms (3.5 kg each), thigh (8 kg each), and lower leg incl. Feet (3.5 ...
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582 views

Determine the point at which moment vector is zero on a 3D body

I have information about total force and moment on a body for three points, whose coordinates I know. From this information I would like to determine the point at which moment would be zero. ...
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Why does the load cause a moment around the support point in column buckling?

Here is a picture from Wikipedia, a free body diagram used to derive the maximum load in Euler's buckling theory. The moment is calculated around point A. It is claimed that the load $P$ causes a ...
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1answer
149 views

Method of joints: The direction of forces

I have the following question: I need to find the load in truss element DF. I calculated the reaction forces at E and D. Fex = 360 KN Fy = 405 KN Then, I used the method of sections at point F ...
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Why is the normal contact force horizontal on an inclined ladder?

There is only one force acting on the ladder which is its weight and it acts vertically downwards. Then why does the normal contact force from the vertical wall act horizontally on the ladder? There ...
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Static equilibrium in an accelerated frame of reference [closed]

TL;DR : I'm trying to resolve an exercice of static equilibrium in an accelerated frame of reference but I do not have the same answer as the correction for the rotation equilibrium. We have an ...
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What holds up the lowest point of a rope following a catenary curve?

A catenary curve is the curve followed by a rope suspended at both ends in uniform gravity. I thought I would try to solve it myself because it seemed like a good challenge, but almost immediately I ...
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3answers
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What is the equation for the tension on the ends of a cable suspended at different heights? [closed]

I'm looking for an equation to find the tension on the ends of a cable suspended between two poles (one higher than the other) with no load but the cable itself. I determined that the tension would ...
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3answers
499 views

Floating objects and fluid statics

If an object is floating, I know about how buoyancy force ($\text {density of liquid} \times \text{volume displaced} \times g$) must equal gravitational force ($ \text {density of object} \times \...
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1answer
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Can there be a moment at a hinge?

I've recently started studying statics and I was told that a hinge cannot offer moment reaction. It offers only reaction forces in x and y directions: But when doing problems I've just encountered ...
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2answers
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Angles in a static equilibrium

I have three masses $\left(F_\alpha, \, F_\beta , \, \text{and} \,F_g \right)$ with 2 pulleys, and a wind variable which is in static equilibrium. I have already calculated the appropriate forces for ...
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How to know what method to use when finding resultant forces?

I am quite confused as to what method should be used when finding resultant forces. Here are two examples of a question that asks to find the resultant force. One requires the parallelogram law to ...
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1answer
171 views

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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1answer
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Mechanics of Material - Forces in a Vertical I beam

Helllo, I was wondering, If I have an I beam like in the rough sketch attached, is the a bending stress that exists in a plane somewhere along the beam? I am thinking there is not since if the ...
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2answers
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Shape of a string/chain/cable/rope/wire? [closed]

The height of a string in a gravitational field in 2-dimensions is bounded by $h(x_0)=h(x_l)=0$ (nails in the wall) and also $\int_0^l ds= l$. ($h(0)=h(l)=0$, if you take $h$ as a function of arc ...
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What's the direction of the static friction force in this free body diagram? [closed]

I know that static friction is a force that opposes any force of motion and in this case we have two: the parallel component of weight force, tension force. So the static friction can oppose the ...
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1answer
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A question about forces acting on an object

https://youtu.be/KWAvj8ATXmE at 2:43 , when he is testing the force by lifting a mass, does he experience the weight of the mass on his hand(as friction) or is it the atmospheric pressure force that ...
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Why don't barbells tip over when a 45 is placed on one side?

A standard barbell is 45 pounds, as is the heaviest weight available in most gyms. When a weight is placed on the side of a barbell, some of the barbell is to the "outside" of the weight, like so, so ...
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Equilibrium in a spoon hanging from a toothpick

While searching about equilibrium I came to this YouTube video which was quite astonishing but the video maker didn't explained the physics behind it. My query is that why the spoons aren't falling? ...

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