# 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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### When we replace supports distributed reaction by point reaction in thin beams, is that considered an application of Saint-Venant principle?

I read about Saint-Venant principle which is about the effect of replacing forces by equivalent forces system that effect on the same small region of a rigid body, all examples I come across are on ...
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### Help with understanding bending moment diagram of a frame structure

I have an exercise where I should calculate and draw a bending moment diagram for a frame structure. The frame structure is similar to the one below, image taken from http://structx.com: I would like ...
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### How is Kyrie Irving body stay balanced in inclined position?

How can we explain this in a scientific way? As far as I understand, your body will stay balanced if the projection of your center of gravity to the ground is still between the area covered by your ...
5k views

### Why are screw holes in most of the door hinges in zigzag orientation?

What advantage does it provide? Explaining with a figure would be helpful. I tried to draw a free body diagram and equated the sum of force and moments to zero, but still was not able to find out.
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### Utilizing symmetry in statics problem

I am given the structure below, and supposed to find the forces occuring in $A, F, E, D, C$ and $B$. The task hints of using symmetry, as several forces are equal in magnitude. Supposedly, $A=B$, and ...
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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 ...
225 views

### 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 ...
465 views

### 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 ...
38 views

### 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 ...
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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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### Cases in finding the maximum weight of the block

I am dealing with this problem about belt and dry friction. I need to find the maximum allowable weight of block B to maintain static equilibrium. I have given value of weight of the block A. The line ...
27 views

### 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 ...
201 views

### 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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### 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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### Diagrams of forces and moments of a statically determinate structure

I'm having difficulties with calculating the distribution of forces and moments in a statically determinate structure shown below. I'm especially confused about the arc part. Will there be only ...
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### Identifying zero force members

My instructor said that if a joint has reaction support attached to it, then it is not a zero force member. However I saw in this figure that joints E and A are attached to a pin and a roller, ...
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### Can I get some help solving this statics reactions problem?

I'm working on this reactions problem. I know M(ay) is equal to 0, but I haven't been able to figure out how to solve for the tension in cable BC, forces A(x) and A(y), or moments A(x) and A(z). I've ...
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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 ...
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### How to simplify a truss bridge diagram?

Hello I have this truss structure question. I understand that we need to determine the zero-force members first so that we can simplify the diagram. But I am not sure which one that I need to ...
749 views

### Why does the upper wing skin fail in buckling and lower wing skin does not?

I am aware of the fact that the buckling is mainly caused in the regions of the specimen which are in compression. But the wing skin doesn't take any axial loads and is used to resist shear, atleast ...
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### Equations of Static Equilibrium

I would like to clarify if the equations that I got from this figure are correct. $$-T_{CD}sin(30) + T_{DE}cos(0) = F_x = 0$$ $$T_{CD}cos(30) - \frac{W}{2} = F_y = 0$$ and -T_{ED}cos(0) + T_{EG}sin(...
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### Centroid and Center of Gravity

I was studying this example but I didn't understand how the author arrived at (A₁ - A₂)G₁G Please I need enlightenment
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### Resultant of coplanar forces

I have a question that goes thus. At what angle $\theta$ must the $500N$ force be applied in order that the resultant $R = 1000N$. For this condition what will.ne the angle $\beta$ between $R$ and ...
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### How to Find the Magnitude of Force and Direction

Give me some tips on how I can find the magnitude of $F_3$. The hint maybe is the angle of inclination of w axis such that the force components are equal along that axis, my instructor once told me. ...
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### Resolution for forces

I'm stuck trying to find the resultant of the force system. Here it is said to find the angle θ the resultant manes with the horizontal. But θ here is narked relative to F₂. How do I find the ...
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### Pump system with dynamic head

Given: A pump system is defined with dynamic head of 46 feet. The height between the static pressure gauge and the surface of the water is 9 feet. Assumptions: Friction losses between the tank and ...
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### Resultant of forces

From the illustration provided on the question, we have the angle between F₁ and F₂ to be 20 deg + 30 deg. But using the formula R = F₁² +F₂² -2F₁F₂ Cosθ to get the Resultant, 130deg was used instead ...
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### Given 3 force measurements, what are estimated forces at other locations?

Given three unequal force measurements spaced equally 120 degrees apart on a circular plate at F_R, F_C, F_L, I need to calculate what the estimated force measurements would be if taken at positions ...
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### Least force required

Relying on my past knowledge on how to attack the problem, I should use the equation Moment of B about AC = $r_{AB} \times B • n^ AC$ To find the least force on B. I just don't know what position ...
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### Finding the reaction force at the hinge

The question given is A uniform rod, of mass $m$ and length $2a$ smoothly hinged to a vertical wall is connected to a point on the wall above the hinge by a light inelastic string. Find the magnitude ...
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### Forces acting on a weightless member

A weightless bar is pinned at the top of a triangle with N weight. Both rests at the horizontal plane. There is a horizontal force F acting on the weightless bar, and a given coefficient of friction μ ...
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### Program name of this buckling modeling

My instructor sent this solving with program that I don’t know the name , does anyone know the name of the program ?
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### Sign of the sum of Virtual work (Direction)

I have trouble understanding Virtual Work (in statics) as I understand what's happening but I do not understand the signs or directions. This is what I know. If the force acts in the opposite ...
6k views

### Why does a gear have extra holes?

In a gear you normally have a center hole for the shaft to be put into. Why do some gears have holes surrounding that center hole? Is it for weight reasons? Does it add stability? Is it so you can add ...
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### Vector expression of bearing pressure

I have been trying to solve the problem below involving a concrete anchor block subject to two equal horizontal forces. Normally I would just apply the force as a moment acting about the centroid of ...
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### Statically determinate structure by adding moment

I'm considering the problem below. It's a setup with a roller joint and a pinned joint with a hinge between the two rigid links. Since there are now 3 unknowns for 3 equations and a zero moment at the ...
597 views

### Calculating angle of a 2D vector with positive y-axis

This has been a burning question that I've been thinking about recently. In statics problems like the one I've attached here where we are asked to find the angle that the resulting vector has with the ...
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### External moment over an hinge

I want to find the moments around points A and B in the following figure. Suppose the structure is fixed at the point where $F_{ax}$ and $F_{ay}$ are located. I consider A and B to be hinges so that ...
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### How to calculate the torque for motors for a Core XY movment?

I am trying to design a simple setup that follows the core XY movement shown: I have been researching the statics behind this movement in order to calculate the minimum torque for the motor so I ...
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### Bending of an L-shaped beam

First post so bear with me: I am designing a frame for a press, which needs to be able to withstand 250 N. I am planning to make the frame an L-shaped beam, turned around. With a side view, it will ...
57 views

### Moment of a force in 3D

The question is not to help me get my task completed. There is the 3D statics problem that I have been attempting to solve for a long time. I have no help, hence I would like to pose you a few ...
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### Statics - other methods for determining reactions of supported beam

Question: Because the question regards the statics, I am going to pose it as well. Are there other methods to solve equilibrium problems other than the method of sections, when dealing with pivots. ...