# 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 physics properties and equations can explain these changes in 3D Axis of Rotation?

Background Programmer whiteboarding to refactor 3D physics engine code that selects pivots and axes based on location and direction of external forces. Consider for example a cuboid lying on the floor....
1answer
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### Why does rotation happens about hinge point in a vertical bar when net force acting on it are zero? [closed]

As we know that if the net external force on a body is zero its center of mass will be at rest and also rotation will happen about center of mass only but in this hinge and rod case it is clear by ...
2answers
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### How does the shear and bending moment diagram relate to the stress tensor field?

I've read a fair amount of material on the physics of elasticity. That mostly covers the states of stress and strain and their relationship at a point. I don't recall ever encountering the so-called ...
5answers
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### How is shear stress different from normal stress?

I feel like I have not understood the difference between these two concepts as well as I thought. My prior understanding of shear stress was that it is stress generated after force is applied parallel ...
4answers
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### Is friction always opposite to velocity?

Let's say an object is sliding on a slope and is the object has a velocity of $(0,0,5)$. The friction would be acting in the opposite direction of motion, being $(0,0,-1)$. However, gravity is also ...
5answers
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### Free body diagram on a rack of wooden blocks [closed]

Considering a rack of blocks, and that I am able to hold it up in a horizontal line without it collapsing. I am trying to draw the free body diagram of one of the blocks in the middle portion, block A....
1answer
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### Constructing a Free Body Diagram (Stacked Blocks)

How can I construct the free body diagram of this figure? I am in a topic of equilibrium of particles so the total force will be equal to zero. The two springs are indicated to give equal forces. Am I ...
2answers
37 views

### Center of gravity of a ring and static equilibrium

We know that the center of gravity of a ring whose mass is uniformly distributed is at the geometrical center. Now if the ring is in a vertical plane and a vertical force against the gravity is ...
4answers
3k views

### Why does the curve of a hanging chain not minimize the area below it?

If we have a chain of fixed length hanging from two points we know that it will form a curve that minimizes the chain's potential energy. If we imagine the chain as having many small segments, then ...
2answers
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### 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 ...
1answer
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### Curvature of sheet due to thermal expansion

I have a sheet of aluminum, 1.2m x 2.8m, which will be bonded to PTFE (also 1.2m x 2.8m). The temperature of the laminate will then increase by ΔT. Material properties are: COEFFICIENT OF THERMAL ...
1answer
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### Statics problem

I'm a math major who's trying to improve some physics, on the topic Statics. Here's the problem: The weighing bowl is suspended on three threads of equal length l. The points at which the threads are ...
5answers
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### Objects falling from table

It is an everyday experience: You have placed an object a tiny little bit too much over the edge of a table and it falls down. This is the case when the center of gravity is above the floor and not ...
1answer
38 views

### 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....
2answers
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### Physics of the Planche

The planche is a gymnastics exercise where the athlete holds their body parallel to ground supported only by their hands. People sometimes train for this exercise using a progression of planche ...
2answers
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### Is there a moment about a frictionless pin

In a structure that looks like this: We have two unknown forces at point A in the x and y directions respectively due to the frictionless pin support, and one unknown force in the y direction at B due ...
4answers
92 views

### Intuitive question about torque formula

Consider two objects as shown: On one side a box with mass 1 kg, 2 m apart from pivot and on the other side two boxes of mass (1 kg each), 1 m apart from pivot, balance a seesaw. This is the question:...
2answers
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### Is the sectioning in method of sections, for truss analysis, arbitrary?

I was looking through a lot of sources about the method of sections. But the thing that stood out to me was that everyone sections a truss such that at least one of the supports, and therefore at ...
1answer
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### This is question is originally in context to elasticity (young mod, bulk mod etc). but i want some clarity on the tension forces (or torque)

I want to know what tension will there be in 2 strings if the are connected by rod and a mass is hung somewhere in between .I somewhat know the concept of torque but I am getting confused here . pls ...
0answers
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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 ...
1answer
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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?
2answers
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### Sand cone in the attic [closed]

My question is based on Halliday books Tom 2, chapter 13 (exercise 42). There is a cone of sand laying in the attic. Consider stress of the floor under the sand cone. Why the biggest stress is in ...
1answer
54 views

### Holding a really heavy object in front of you

If you have inhuman strength, is it possible to hold an object way heavier than you with your arms forward horizontal while standing with no anchoring? Or will the object simply make you fall forward ...
1answer
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### Static Analysis of a Diagram

It is very clear $M_A$ can not be zeros under general loading conditions, so this structure must be able to rotate about A. but the geometrical constraints will not allow it to undergo this rotatory ...
1answer
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### Why is tension on both ends of rope equal and why is it only achieved at the middle of the rope when the mass is suspended by a ring?

I was told that when a mass attached to a smooth suspending wire by a ring shaped holder; after reaching the equilibrium position it would be exactly halfway across the wire and, tension on both ends ...
3answers
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### Stability analysis basics

I would like to see a rigorous treatment of stability analysis. For example, a lot of high-school level texts give examples like this: https://courses.lumenlearning.com/physics/chapter/9-3-stability/ ...
0answers
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### Moment on a rectangular concrete slab

Here is a picture from my engineering textbook. It describes a concrete slab being subjected to normal force $P$ and a certain moment. The moment is expressed by the normal load $P$ affecting at some ...
1answer
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### Suspicious of Khan Academy's answer for a simple tension on a clothesline question [closed]

This is the question: 3 kg of wet clothes are hung on the middle of a clothesline with posts 6ft apart. The clothesline sags down by 3 feet. What is the total tension upon the clothesline? They give ...
4answers
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### Does a planar object balance on a unique point?

Consider a horizontal planar convex 2D object (say lying on x-y plane) with uniform density. Under constant gravitational force (say in -z direction), does it always balance on a unique point lying ...
1answer
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### What does the vertical plane which passes through the the line of the greatest slope of an inclined plane represent?

I encountered a problem while solving a question about friction force regarding static bodies The question is as follows, "A body of weight $W$ is placed on a rough plane inclined to the ...
2answers
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### Calculate Tipping Force of Table [closed]

How do you calculate the force it would take to push over/lean on a table for that table to tip. The table top is 144" X 40" and weighs 281 lbs. The table is supported by (4) table bases ...
0answers
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### Distribution of weight among massless strings hanging a rod of uniform density

Let the mass of a rod of uniform density be $W$ and its length be $l$. Several massless strings have been used to hang the rod at positions $x_1, x_2, ..., x_n$ where $0 \leq x_r \leq l$. Find ...
1answer
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### Why is the normal force of a traffic light pole merely exerted by the right bolt?

In reference to a recent statics problem, please see inserted picture for the correct situation below, it was required to find the magnitude of force ($F_3$), exerted by the leftmost bolt on the ...
2answers
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### Friction on a rod resting against a rough horizontal rail? [closed]

In which direction does friction act on a rod leaning on a rough horizontal rail, where the normal force is perpendicular to the rod and the rod has its bottom end on a smooth horizontal floor with ...
1answer
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### Conditions for equilibrium on a hexagonal pencil [closed]

A hexagonal pencil lies on a slope with inclination angle α; the angle between the pencil’s axis and the line of intersection of the slope and the horizontal is φ. Under what condition will the pencil ...
1answer
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### Mechanical Advantage of Static Double Pulleys

For a set of two double pulleys, the force acting on each should be equal to the tension in the rope times the number of ropes connected to the individual pulley if I understand correctly. In this ...
1answer
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### Strength of wall regarding a system of hanging mass

When we assume that mass m is directly at the center of L, and $\alpha$ is the angle between the rope and the horizontal, I am able to show that for equilibrium, $$\sin{\alpha}=\frac{m}{2M}$$ There is ...
0answers
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### Shortcut to a problem based on toppling using D'Alemberts Principle [duplicate]

I found this question on this very site and was curious on how to solve it using D'Alembert's Principle Here's the link to OP(link) .I already know how to do it by balancing the torque about toppling ...
2answers
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### An equation related to lever

To balance a lever, as we know, fulfills $f_1l_1=f_2l_2$, what is the condition that fulfills both $f_1l_1=f_2l_2$ and $f_1+l_1=f_2+l_2$?
1answer
56 views

### Horizontal tension in hanging rope with mass [closed]

If we have a hanging rope with mass so that it forms a catenary, from what I have read, the horizontal tension in the rope remains constant. I also have seen that the equation of a catenary depends on ...
0answers
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### Does an elastic massy hanging chain take the shape of a parabola?

This is a problem in "Differential Equations: A Modern Approach with Wavelets" by Krantz: If the length of any small portion of an elastic cable of uniform density is proportional to the ...
1answer
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### Geometry of deformation of Axial members connected to a rotating rigid element

On axial members connected to a rotating rigid element, we have the following relationship $$\frac{-\delta_1}{a}=\frac{\delta_2}{b},$$ which is based on the concept of similar triangles. In the ...
2answers
299 views

### Tension in Common Catenary

I was reading the intrinsic equation of common catenary , where the author assumes tension in the catenary and proceeds. Why does a freely hanging rope with uniform mass per unit length has tension ? ...
1answer
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### Position of resultant of two like parallel forces

I am solving Statics and stuck in middle of a trivial understanding. Let us say we have two like parallel forces acting on a rigid body . Force P has point of application as A and Force Q has point of ...
2answers
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### Expression for force of gravity on an arbitrary curve with endpoints fixed

Consider the following problem: A frictionless tube lies in the vertical plane and is in the shape of a function that has its endpoints at the same height but is otherwise arbitrary. A chain with ...
3answers
239 views

### Can you calculate the force of chair legs on floor?

I have kinda formalistic question. Eg. we have normal symmetric chair with 4 legs, and mass $M$. Can we calculate forces of chair legs on floor surface $F_1,F_2,F_3,F_4$ with only this data and why ...
2answers
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### Question on statics

Consider a uniform beam that is supported by 3 pivots that are the same distance from each other (shown below). What will the normal force exerted by each pivot be? The situation seemed rather ...
1answer
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### Static equilibrium problem [closed]

I am designing a balanced-arm lamp structure for a robotics project and I obviously want the lamp to stay on its base without falling when the arm is extended. For that, I applied the conditions for ...
3answers
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### Measurement of force (statics) [closed]

body 1 and 2 are pulling the balance by 20 N what does the balance read? same question but without 2. for 1st question I thought the balance will read zero force because they are two opposite forces ...
1answer
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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 ...