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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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...), ...
Yoda's user avatar
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4 votes
3 answers
337 views

Proper treatment of springs in special relativity

I've looked on-line for a simple treatment of springs under tension/compression while moving at relativistic velocities parallel to the direction of tension/compression and could not find one. There ...
Stevan V. Saban's user avatar
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1 answer
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On beam suspended by wires

My question involves sample problem 9-8 of the book "Physics" by Halliday, Resnick and Krane, 5th edition. So I could understand the answer given but there is something that is not ...
Ruben's user avatar
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1 answer
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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.
Olivia's user avatar
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-1 votes
2 answers
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Adding mass to a bowl until it sinks [closed]

I've been struggling with this question. A hemispherical bowl of inner radius $r$, density $ϕ$ and thickness $t$ is floating in a fluid of density $ρ$. The bowl is being filled with sand at a constant ...
Developer's user avatar
2 votes
1 answer
264 views

Calculating the sag in a cable that has two different weights (two wires joined together)?

I'm familiar with the equation for the sag of a cable: $$x = \frac{wx(L-x)}{2T}$$ Where w = the weight per length, T = the tension and L = the length of the span between supports. I'm wondering if ...
am1234's user avatar
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Tensions in the chains [duplicate]

What is the physics behind this mechanism? What would be the free body diagram be like regarding all the magnitudes of the tension forces present in the chains?
Jacob Lee's user avatar
2 votes
2 answers
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Tensions in the chains

What is the physics behind this mechanism? What would be the free body diagram be like regarding all the magnitudes of the tension forces present in the chains?
Jacob Lee's user avatar
1 vote
1 answer
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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
0 votes
2 answers
50 views

Direction of the normal force [closed]

Suppose we have a bar with non-zero mass inside a hemispherical bucket fixed to the ground. Suppose, too, that there is friction between the bar and the inner spherical surface of the bucket. Part of ...
Rafael Ferreira's user avatar
2 votes
0 answers
52 views

Stability of a pile of dominoes [closed]

Consider the above figure; $n$ identical uniform dominoes, each of length $l$, are stacked upon each other in the presence of a uniform gravitational field. Find the maximum distance and the setup for ...
Cognoscenti's user avatar
4 votes
1 answer
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Computing the strain in a cantilever beam under a known deflection

I intend to use a cantilever beam to calibrate a strain gauge, in a setup similar to the picture. My idea is to introduce a small known vertical displacement $\delta$ on one side of the cantilever ...
user386164's user avatar
-1 votes
1 answer
67 views

Static equilibrium of linkage [closed]

I have a question regarding the calculation of the forces of a linkage in static equilibrium. Consider the mechanism in the figure. Points A and B can move in all 3 directions (hence they have 3 DoFs ...
Jorge's user avatar
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0 answers
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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 ...
John 's user avatar
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1 vote
2 answers
117 views

Why can multiple eggs support more weight per egg when there are more of them?

In this video by TAMU Physics & Astronomy titled "Eggs can support A LOT of weight!": https://www.youtube.com/shorts/a7JvE-fGrgg?feature=share The teacher first grabs an egg and places ...
Aequitas's user avatar
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1 answer
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Accelerating fluid making an angle with horizontal [closed]

The proofs of the two equations (1) and (2) below are given at the end of this question in the last image. $$\frac{dP}{dy} = -ρg$$.......... (1) Where P is pressure and ρ is density of fluid. $$\frac{...
Apoorva Shukla's user avatar
12 votes
6 answers
1k views

Is the weight of something being dropped the same as the force of something being static?

If I have a block of let's say: 10 kg and I put it over my foot in a static manner, what we know from static mechanics is that my foot is opposing the weight of the 10 kg mass with the same force in ...
Gabriel Nieto's user avatar
0 votes
1 answer
58 views

How to calculate normal force acting on part attached with a screw? Can the force on screws be decreased by lowering the height of the normal force? [closed]

I have an L-shaped beam (equal height and width lengths) hanging from a screw on the wall, and I model the screw as a pin joint (hopefully okay approximation even though it does apply a constant force ...
Sven Voigt's user avatar
0 votes
1 answer
52 views

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 ...
Spluesh's user avatar
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1 vote
3 answers
63 views

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?
user16629503's user avatar
0 votes
1 answer
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Origination of internal forces in a beam under axial loads

Take a prismatic beam and subject it to a tensile loading, assume we are applying a load of 10 N on both of its ends. As we know, the beam stretches by a certain amount on either sides. And since ...
Jeffy James's user avatar
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0 answers
53 views

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 ...
Ken Adams's user avatar
0 votes
0 answers
62 views

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 ...
Jeffy James's user avatar
1 vote
0 answers
28 views

How to calculate longitudinal force on two rods where each is fixed at one end to the ground and connected to each other at the other? [closed]

Imagine a 2D scenario. There are 2 rods. Both are fixed at one end to the ground (some distance away from each other). The connections to the ground are universal joints that are free to rotate. The ...
amortaza's user avatar
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1 vote
1 answer
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Finding the tipping force for a cantilever table [closed]

How would I find the force it takes to the table to tip over if you were sit on top the cantilever end?
Thunderrob's user avatar
1 vote
2 answers
121 views

Weight distribution and support polygon

I was working on a problem of supporting an object with sticks and wondering about some use cases that would fail. My approach is to place the n-sticks (for example 4) under an object with mass m ...
Ken Adams's user avatar
1 vote
1 answer
117 views

Vectors forming a closed triangle

I've always been taught that vectors that form a closed polygon represent an object being at equilibirium, that is there is no resultant force on the object. However, this has never been intuitive to ...
Jeremy Clarkson's user avatar
0 votes
0 answers
61 views

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 ...
user695849's user avatar
0 votes
1 answer
99 views

Is it possible to find the forces in this problem involving a block/beam/bar glued to the side of a wall?

This is a follow-up to a previous post of mine post. In that post, we concluded that a beam cannot be held in place by an application of normal forces in only one location if that location is off the ...
Maximal Ideal's user avatar
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1 answer
71 views

Horizontal bar with one fixed end held by support beams touching/"pinching" it at one location to keep it from falling — Unsolvable problem?

Suppose we have a horizontal rigid bar held in place by two reinforcement beams (one above the bar and one below the bar), both of which are attached to a wall, such that they "clamp" the ...
Maximal Ideal's user avatar
1 vote
0 answers
104 views

Please help me understand what the tipping point of this Pedestal Table will be? [closed]

I am brand new here. I am a furniture maker and designing an Oval Pedestal Table for a client. I presented a design that I felt comfortable with, however my client has asked that I shrink the ...
Richard's user avatar
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1 vote
2 answers
44 views

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,...
Julius Cheezer's user avatar
1 vote
0 answers
55 views

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
1 vote
1 answer
101 views

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 ...
user5588495's user avatar
20 votes
7 answers
5k views

Plank overhanging off a building — where does the normal force go?

Suppose there is a (uniform rectangular) plank of mass $m$ and total length $L$ that is on top of a building with some piece overhanging or jutting out past the building. Assume it isn't past the ...
Maximal Ideal's user avatar
0 votes
0 answers
41 views

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 ...
Ash's user avatar
  • 71
0 votes
2 answers
74 views

Parallel and concordant forces

I translate into English what is written in Italian in the adopted text. Two forces are parallel if they have parallel lines of action; two parallel forces are concordant if they have the same ...
Sebastiano's user avatar
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4 votes
3 answers
262 views

Vectorial sum of two parallel and discordant forces

To obtain the resultant force, colored in purple, of two parallel and concordant forces $\vec{F_1}$ and $\vec{F_2}$, I apply a vector $\boldsymbol f$ (colored in brown) to the bar $AB$; similarly ...
Sebastiano's user avatar
  • 2,519
1 vote
2 answers
322 views

Acceleration of an object after overcoming static friction

Let us imagine a rough horizontal surface with static frictional coefficient $u$ and an object of mass $m$ sitting on that surface. The maximum static frictional force that can be applied is $uN$ ...
madness's user avatar
  • 1,185
3 votes
4 answers
463 views

Proving an intuitive fact rigorously

We place a wooden stack upon two supports and place a weight of mass $m$ at one of its ends. Now it is almost obvious intuitively that just at the verge of the mass $m$ falling down, the normal force $...
madness's user avatar
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0 votes
1 answer
133 views

Why the harmonic series appears when we stack a pile of books?

lets say we have some books resting on the floor.I am trying to find the maximum protuberance that the books can achieve.we see that the books on top of the initial book must have the center of mass ...
Pulsar Plasma's user avatar
0 votes
1 answer
157 views

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
0 votes
1 answer
91 views

What is the minimum vertical length of contact with the wall needed for an object to stay attached to a wall with an electrostatic force?

Say there's an object, a rectangular prism, that becomes electrically charged and then stuck on a wall using the electrostatic attraction between the object and the wall. The object and wall are ...
Nathan Czopp's user avatar
3 votes
0 answers
69 views

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?
Dekka's user avatar
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3 votes
2 answers
396 views

Is weight distribution influenced by the location of the weight's attachment points (see drawing)?

Is there any difference in terms of fore/aft weight distribution between the two wheels in the two pictures? In other words: Is the location of the center of gravity of the 100kg weight the only ...
aehhhhmm's user avatar
3 votes
1 answer
97 views

Where do these forces come from?

Lets say a door is entirely supported by two hinges, one at the bottom corner and one at the top corner. I know that the two vertical forces of the hinges are produced by newton third law, however ...
VOZ ESTOICA's user avatar
0 votes
2 answers
149 views

Why does a beam balance restore? [duplicate]

This question was previously asked 11 years ago here, but I believe it does not answer my question for the following reasons: (A) The first answer takes a different system, mine looks like this. (B) ...
CallousCalculus's user avatar
0 votes
1 answer
222 views

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 ...
Krys's user avatar
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1 vote
3 answers
127 views

Why can't I use $\tan()$ to find the force of tension within a rope that forms a triangle? [closed]

Apologies if this is too simple, but my teachers could not give me an answer. The following is a question from my grade 12 physics homework: Now, the solution for $T_2$ is simple: $T_{1_x} =T_{2_x}$ $...
Kiril B's user avatar
  • 13
0 votes
4 answers
113 views

Equilibrium on a plank

Consider the classic scenario of an equilibrium with a man standing at the centre of the plank, with the plank being held up by two trestles, say the man exerts a force of 500N at the point he is ...
Vivaan Daga's user avatar

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