# Questions tagged [statics]

Statics is branch of engineering concerned with the analysis of forces and moments on physical systems in static equilibrium.

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### Stress concentration

Let's say we are using an aluminium with a yield and ultimate stress for an element like this: In this case we will get some stress concentration around the fillet due to the change of area, however, ...
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### Where does this support reaction come from?

I am looking at part a of the following question, and I can not figure out where this support reaction N is coming from. The solution is as follows. The question and diagram make no mention of N. My ...
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### Problem of lifting of a body using 4 strings

I have a solid object that has been lifted to a hieght by 4 strings. I know the lifting point and the 4 corners of the object. Also the mass and the center of the gravity location of the object is ... 1 vote
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### Equilibrium problem with 3 unknown forces | Hanging mass

This problem is related to my previous question on the generalized Lami's theorem. I would like to see how you solve this problem and compare with my solution. My motivation for this problem is that I ...
1 vote
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### how to determine the direction of support reactions in a truss?

Hi, I am not sure how to determine the direction of support reactions at point A and K. I know point A has a pin support, therefore, it can take in horizontal and vertical loads and point K has a ... 1 vote
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### Is there a way of "shortening" a mechanical lever, but keeping its mechanical advantage intact someway?

For what I think I know, the mechanical advantage of a lever comes in exchange for the distance the load travels upwards, independent from the type of lever (I think). So, let's say, in a (class-1) ...
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### Could a hybrid system of mechanical levers and hydrostatic/hydraulic cylinders be able to lift 200+ kg with the force of an arm?

I don't know much about levers and hydrostatic/hydraulics myself, so I hope I don't make too many misconceptions. The idea: Hypothetically, if you had a 40km+ long indestructible lever on a ...
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### How to calculate forces on bearings in a chain drive

I have a chain drive which is moving a load of 200kg. I have 95Nm on the input shaft which has 15 teeth, which results in 152Nm on the output with 24 teeth. The shafts are supported on bearings on ...
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### Best way to deploy a projector screen from the bottom?

I want to design a system for an electronically deployable projector screen, where when not in use the screen is stored at the bottom and there are no structural elements sticking up significantly, ...
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### Mechanism and static determinacy

I was doing exam question and am confused as to how to determine if the structure is a mechanism or not. Say that j = number of joints, r = total number of reactions, b = number of bars. For both (a) ...
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### What are the physics behind a TV wall mount?

As I was installing this wall mount, I began to wonder how exactly physics is at work with it. In other words, how does the design of the mount play a role in ensuring that the mount itself supports ...
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1 vote
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### How to solve this complicated truss system?

Below is a truss I simulated in a truss calculator. I'm just wondering, how to solve for the compression and tension of each member and are there any method that can solve this? My solution is I ...
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### Equations of condition: why are two moment equations around a hinge dependent?

I'm reading about static determinacy of structures here. A quote: Therefore, one extra equilibrium equation is added to the system due to the introduction of the hinge: either ∑MABB=0 or ∑MBCB=0. ...
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1 vote
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### How to replace these two forces with one force?

Here, $P>Q$. $O$ is the center of mass of the rigid and uniform bar/stick. As $P>Q$, the resultant is situated to the right of $\vec{P}$ and is parallel to $\vec{P}$. The magnitude of the ...
1 vote
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### should the hachures in moment and shear diagram be vertical?

when we plot the shear or moment diagram we add hachures to the area created with these diagrams , in most cases we see vertical hachures, is it represent the internal forces? or its just used to ...
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### Mechanics Statics: verifying reactions at supports

Figure (a) shows the problem and (b) the free-body diagram. The question is to verify the reactions at C and E. I understand the remainder of the free-body diagram but do not see how C and E are ...
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### Why do we always need to calculate the 'Moment of Inertia' about neutral axis for bending?

I was having a look at the bending stress derivation in few of the books. The derivation indicates how each of the element in the bending stress equation is derived into that equation. However, for ...
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### How exactly do forces transfer in different directions?

If we imagine the load being placed at the top of the below triangle, I realise that the downwards force is transferred into one which goes in a 'south east' and 'south west' direction down to the end ...
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### What are the units used in beam bending equations? Do they matter?

I was just wondering whether or not the standard beam bending equations worked for all units. E.g. imperial and metric etc. From what I'm guessing it shouldn't really, since once we plug everything in ...
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### Can a beam be too short to experience bending stress?

The question in the title says it all. I've got a a configuration where I'm using a bolt to support a load. The way its set up, the bolt will have a very short cantilever on it. When I calculate the ...
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### How to determine beam deflection with this unusual configuration (diagram attached)

So I've got a support system shown here in the attached image. Comparing configuration "A" to "B" it seems intuitive that "A" could support a larger load. The stubs are ...
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### Is an axial force applied at the centre of a beam considered a compressive force, tensile force, or both?

I was looking through some course notes and realized that I never fully understood this concept. So, looking at the diagram below we can see that there is a 20kN axial force being applied in-between ...
1 vote
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### What is the difference between a sum of moments about a point versus the moment at a point?

In class we're learning about moments, and I'm not entirely sure what is the difference between using an equation of equilibrium for the moments about a point (in this case C), and the actual moment ...
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### A Bonus homework question in Elementary Statics. A painter on a ladder put on a ledge [closed]

we have been asked about a bonus question in Basic Statics as mentioned below. I would be glad if someone help me with it. The question is: There is a painter which is going to work on a ladder as ...
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### Friction in Wedges: finding the mass of the block C on the verge of slipping

I need to solve for the mass of block C that is in the verge of slipping. All surfaces have a coefficient of static friction of 0.11. The cable connecting the wedge B and C is parallel with the ...
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### Determining the Angle based in Tension

I am trying to solve the following problem, but got lost in the process. I am trying to find the minimum/maximum angle ( θ ) needed to have the system in equilibrium without breaking the ropes which ...
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### How do you calculate the shear force on the screws that connect a door to a jamb via hinges

I'm trying to calculate the shear forces on hinge screws or bolts. Here is a schematic of the door with the relevant values: First, I took a free body diagram of the door and its hinges. The ...
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1 vote
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### What size feet for this wind-protection panel?

I need to create a series of free-standing perspex panels to add height to an existing fence for wind-proofing purposes. My idea is that each panel would be fixed to two supporting poles that are ...
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### Machine Analysis Problem: Finding the vertical force at joint K

Help me in determining the right solution in this problem. I already have an initial solution here but when I compute, my answer does not match to the answer key. I would like to know where did I ...
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