What is Statics: Definition and 902 Discussions

Statics is the branch of mechanics that is concerned with the analysis of (force and torque, or "moment") acting on physical systems that do not experience an acceleration (a=0), but rather, are in static equilibrium with their environment. The application of Newton's second law to a system gives:






F


=
m


a



.


{\displaystyle {\textbf {F}}=m{\textbf {a}}\,.}
Where bold font indicates a vector that has magnitude and direction.





F




{\displaystyle {\textbf {F}}}
is the total of the forces acting on the system,



m


{\displaystyle m}
is the mass of the system and





a




{\displaystyle {\textbf {a}}}
is the acceleration of the system. The summation of forces will give the direction and the magnitude of the acceleration and will be inversely proportional to the mass. The assumption of static equilibrium of





a




{\displaystyle {\textbf {a}}}
= 0 leads to:






F


=
0

.


{\displaystyle {\textbf {F}}=0\,.}
The summation of forces, one of which might be unknown, allows that unknown to be found. So when in static equilibrium, the acceleration of the system is zero and the system is either at rest, or its center of mass moves at constant velocity. Likewise the application of the assumption of zero acceleration to the summation of moments acting on the system leads to:






M


=
I
α
=
0

.


{\displaystyle {\textbf {M}}=I\alpha =0\,.}
Here,





M




{\displaystyle {\textbf {M}}}
is the summation of all moments acting on the system,



I


{\displaystyle I}
is the moment of inertia of the mass and



α


{\displaystyle \alpha }
= 0 the angular acceleration of the system, which when assumed to be zero leads to:






M


=
0

.


{\displaystyle {\textbf {M}}=0\,.}
The summation of moments, one of which might be unknown, allows that unknown to be found.
These two equations together, can be applied to solve for as many as two loads (forces and moments) acting on the system.
From Newton's first law, this implies that the net force and net torque on every part of the system is zero. The net forces equaling zero is known as the first condition for equilibrium, and the net torque equaling zero is known as the second condition for equilibrium. See statically indeterminate.
A physicist who does research in statics is called a statician.

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  1. lc99

    Statics free body diagram (frames and machines)

    Homework Statement Homework Equations Trying to find the reaction forces at E. But, I am kinda confused about drawing the free body diagram for each member. I know that member AD and CB are two force members. What is wrong with my free body diagram then? The Attempt at a Solution i...
  2. jybe

    Force Acting on Hinge: 2744 N Torque on Beam Homework: Find Force on Hinge

    Homework Statement "A beam of mass M = 280kg and length L = 2.2m is attached to a wall with a hinge (at a 90 degree angle to the wall, sticking out horizontally), and is supported at the other end by a wire making an angle of 30 degrees with the horizontal beam. What is the force acting on...
  3. Tirijazzmanray

    Statics problem -- Stability analysis of a slab resting on an incline

    Dear colleagues: My name is Ignacio Pérez, a mining engineering student from Spain. I am trying to analyze the stability of a slab with rounded edges against a toppling failure. The slab can be considered rectangular-prism shaped (I provide a rectangular section in the enclosed picture) but the...
  4. S

    Why does ENGR Mechanics: Statics cover *hinged* trusses?

    Something that has always been off for me is the canonical pedagogical treatment of analysis of trusses in the course typically called "Engineering Mechanics: Statics". Certainly, every cantilever bridge I see has completely attached joints, although lately I have seen some airy, open...
  5. lc99

    [First Year Statics] Replace Force System

    Homework Statement Homework EquationsThe Attempt at a Solution [/B] the force resultant = (100i +620j +800k) = 379 N moment result is (100i-620j+800k) = 1017 which is not correct! I calculated the moment of all forces about point O using cross product so... (-3i + 2j) x (-200j) + (-3i +2j) x...
  6. lc99

    [First Year Statics] Find equivalence location of system

    Homework Statement Part C ) help Homework Equations So far.. Moment resultant = 1800i +3200k , magnitude = 3070 N*m Force resultant = 500i +300j + 800k , magnitude = 990 N The Attempt at a Solution For the location, I'm not getting x = 1.16, y =2.06. Instead , I am getting Mx = Fr*y --> y...
  7. lc99

    Simple Equivalence Problem- help please (First Year Statics)

    << Mentor Note -- Thread moved from the technical forums, so no Homework Template is shown >> Okay, so i am having severe problems with figuring out what i did wrong... I am given : F1 = 250 and F2 = 90 The correct Force result is = 245 i +228 j with magnitude of 335 . The moment given is...
  8. blixel

    Trigonometry: Another Statics Problem

    Homework Statement A subdivision lot is 200 ft long by 80 ft wide. A surveying crew made an error of 0.10 degrees when setting the iron pin in the corner of the lot shown. By what distance is the correct pin off of the true corner? Homework Equations I think I'm doing this one right...
  9. blixel

    Trigonometry: Wanting someone to check my answer for Statics

    Homework Statement A building is 400 ft tall and has suffered damage from a recent earthquake. If a surveyor is stationed 150 ft away, sets a zero angle on the bottom corner of the building, and turns the angle shown to the top of the building; what is the angle at which the building is leaning...
  10. M

    Automotive How do I solve a 3D problem involving a trailer and wheel sizing using statics?

    Hi all, I have a problem with a 3 wheel trailer and sizing the wheels. Using statics, how would I solve this 3D problem by breaking it down? The trailer is sitting on rectangular section and a plate on top carries an even load of 3500kg (roughly 35kN) If I take a cross section A-A and try and...
  11. M

    Bending Moment Statics Solving

    Homework Statement https://imgur.com/a/AGJaN It's a project so not a textbook question. The Attempt at a Solution Given in imgur picture. [/B] I'm looking to solve for C. The problem is actually a trailer with 3 axles but simplifying here as 3 fixed points where the wheels would be. The...
  12. F

    Determine the vertical reaction force

    Forgive my current brain fart, but just posting here for some confirmation of my thoughts. I have a cart with a similar setup to a rear wheel wheelbarrow. Assuming static conditions, I am trying to determine the vertical reaction force (FA) from the ground when applying a horizontal force to...
  13. M

    Statics of structure, distributed load

    Homework Statement All data are in the image uploaded Homework Equations I don't know how to deal with two confounded loads The Attempt at a Solution I really need fast replies thnak for your attempt
  14. M

    Solving Statics Deformation Problems: Rod Equations & Attempt at Solution

    Homework Statement Homework Equations deformation=(force*length)/(elastic moduli*area) The Attempt at a Solution and since most of the variable are constants it seemed like a simple plug in problem, however it seems that my use of the forces is incorrect. unfortunately we had no examples...
  15. M

    Automotive How to find the uneven weight distribution on 4 wheels

    Hello, I am working on a project where I am trying to find the weight distribution on a 4 wheeled vehicle that is traveling diagonally up an incline. You can effectively think of the vehicle as having a pitch and a yaw angle in the body frame. Using an arbitrary location of the total center of...
  16. F

    Statics rigid body equilibrium

    What does it mean where it says it provides couples on x-axis and z axis? Anyways what am I doing wrong? my procedure is finding tension in cables by summing moments about point A. then with the tensions, finding reactions at A. However when i sum the moments about A I get 3 equations 2...
  17. lichenguy

    Conceptual question about frictional force and equilibrium

    A uniform beam of length L and mass m is inclined at an angle θ to the horizontal. Its upper end is connected to a wall by a rope, and its lower end rests on a rough, horizontal surface. The coefficient of static friction between the beam and surface is μs. Assume that the angle θ is such that...
  18. F

    How can I draw the resultant force of the couple M, F1 and F2?

    I'm supposed to express the reultant force R of M, F1 and F2 in terms of F1, F2, r, s and α. But I need to know how to draw R first. How can one do this? Does the couple create a force uppwards from O? Can I move F_1 and F_2 also to the origin and combine the forces? Here is the image:
  19. F

    Pin A & C: Why No Y Component in Solution Manual?

    Homework Statement Pin A and C are the same, however in the solution manual it shows that C does not have a y component. Why is that? Homework EquationsThe Attempt at a Solution
  20. F

    What Does No Axial Thrust on Hinge B Imply in Statics?

    Hello, i"m having a little trouble recognizing the reaction forces in 3d. To begin what does it mean when the question states "assume there is no axial thrust on hinge B?" on the following question. don't know how to upload picture here but there is a sheet of plywood on the ground and the there...
  21. M

    MHB Statics for rod attached to string

    could someone please explain to me why there is no relative force at point a where the rod ab is attached to a thanks
  22. T

    Understanding Tension on a Pulley

    Homework Statement Problem image: https://prnt.sc/gvhjso In this case I have to find the reaction forces at the point E (the Fx, Fy, and the Moment at point E) by using the given data. The 20kN forces at the load AC are concentrated, and are 1.8m far from each other. The tension of the cable is...
  23. D

    Finding Equilibrium in a Weightlifting System: Torque and Statics Explained

    First of all, I will like to say that I'm teaching myself physics because I've never learned it at school. So, please excuse my ignorance and bear with me. This is not really a homework problem but rather a problem I thought on my own given a situation in real life. 1. Homework Statement...
  24. H

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    In the following diagram, a frictionless disc is supported by a massless string. This problem was given by the author of a book, and a solution was given to some questions that were asked about this diagram. One thing the author said in one of the solutions, was that the tension in the string...
  25. J

    Statics Problem involving blocks, rope, pulleys and springs....

    Homework Statement The angle at the bottom is 25 degrees Homework Equations Springs Parallel; keq = k1 +k2 Sum Forces = f1 + f2 x = f1/k1 = f2/k2 Springs Series; 1/keq = 1/k1 + 1/k2 Sum x = x1 +x2 F = k1x1 =k2x2The Attempt at a Solution Basically I'm having trouble finding the spring...
  26. H

    Fluid Statics- u-tube displacement

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  27. B

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  28. X

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  29. X

    Calculating Unknown Forces in a Vector Diagram

    Homework Statement Hi, I'm having trouble with my first mechanics assignment and I'd appreciate some help. So, an object is being pulled using two ropes (Fa and Fb) with a resultant force of 970 N along the x axis. Angle from Fa to the axis is 20 degrees, angle from fb to the axis is 51...
  30. Kaura

    Solve F2 Components & Find Magnitudes U & V Axes

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  31. marsupial

    Equivalent force and couple moment

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  32. D

    Learning Statics: Resources to Expand Your Understanding

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  33. C

    Finding forces in members of frames

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  34. M

    Scalar Moment around a point due to a force

    Homework Statement In two dimensions, the moment of a force can be calculated using the scalar method, MO=Fd, where F is the magnitude of the force and d is the perpendicular distance from the line of force to the point where the moment is being considered. Using the scalar method, calculate...
  35. B

    Moment Equilibrium in terms of box weight

    Homework Statement The board shown below is being held in equilibrium in the vertical plane by three smooth rods at A, B, and C Determine the magnitudes of forces at A, B, and C in terms of the weight of the body, W. Homework Equations Moment = f*r Here's a diagram The Attempt at a...
  36. S

    Statics: pushing a block up a wall w/ friction

    Homework Statement They ask for the smallest force P to apply if neither block is to slip. Coeff. of friction given as 0.25. The 20KG block is 196N; the 10KG block is 98.1N [/B]Homework EquationsThe Attempt at a Solution [/B] If we start at the 10KG block: Sum of forces x: N + cos26.6P –...
  37. F

    Statics on an inclined plane

    Homework Statement On an incline with slope angle α there lies a cylinder with mass M, its axis being horizontal. A small block with mass m is placed inside it. The coefficient of friction between the block and the cylinder is μ; the incline is nonslippery. What is the maximum slope angle α for...
  38. A

    Courses Thoughts on Taking Statics, Physics, Calc 4 in one quarter

    Hey guys. I'm wondering if this is too heavy of a course load. I am studying construction management, but I'd like to minor in mathematics. I really enjoy math and science, and do well in all my classes. I want to finish the calculus series, but after this quarter I will not have the time. To...
  39. Aslet

    A spring-mass system in circular motion

    Homework Statement I uploaded the image of the system to have a visual example. : ) A point mass ## m ## connected to a spring is bounded to move on a circular guide with radius ## R ## without friction. The guide is fixed to a vertical plane and the other extremity of the spring is attached at...
  40. B

    Help with Statics Friction Homework: Not Getting Right Answer

    Homework Statement Homework Equations Sum of forces and moments The Attempt at a Solution Not getting the right answer. Dont know where I went wrong.
  41. W

    How to calculate the tension in a beam of a bridge?

    Homework Statement A bridge, constructed of 11 beams of equal length L and negligible mass, supports an object of mass M as shown in the picture. Assuming that the bridge segments are free to pivot at each intersection point, what is the tension T in the horizontal segment directly above the...
  42. T

    Statics and Rotational Dynamics

    Homework Statement A thin walled spherical shell with a mass of 0.605 kg and a radius of 0.0402 is released, from rest, at the top of an incline. The spherical shell rolls down the incline without slipping. The spherical shell takes 7.49 s to get to the bottom of the incline. A solid sphere...
  43. N

    Can a Cantilever Beam with a 20 lb Mass Hold Up without Failing?

    What's happening Form, It's been a while since I've done a FBD, but I wanted to get someone's input here and tell me if my math/logic is correct. I want to install a cantilever steel beam with a 20 lb mass at the end of it. I'm using carbon steel ASTM A108 (cheapest steel on McMaster-carr). I...
  44. R

    Finding Forces in Member AE & AB: Exam Follow-up

    Homework Statement Determine all member forces and state if they are in tension or compression, in particular I am looking for member AE and AB[/B] Homework EquationsThe Attempt at a Solution Ok so we are supposed to redo the problems from our exam, only I can't figure out how to find the...
  45. S

    Statics: force to open a door on 2 rollers given friction

    Homework Statement We have a 200-LB door hanging from 2 rollers, A & B, which are 5 feet apart. Coeffs of friction for A and B are .15 and .25, respectively. A force P is applied to the door. How big must it be to move the door to the left?[/B]Homework EquationsThe Attempt at a Solution I...
  46. O

    Why does the Principle of Virtual Work work without higher math?

    The last chapter of most introductory textbooks on STATICS introduces VIRTUAL WORK. It is rarely taught (I studied the syllabi of colleagues). I understand the Principle of Virtual Work, having researched and studied the Calculus of Variations, Hamilton's Principle, the Lagrangian and related...
  47. Vanessa Avila

    Statics: Method of Joints (Truss)

    Can someone explain to me why that highlighted force is 0? Homework Equations ∑Fx = 0 The Attempt at a Solution I found FDC to be 780lb and I am still trying to solve for FDE
  48. F

    Projection of Resultant Force: Why Do We Need to Add B-Component?

    Homework Statement What's the projection of the resultant force onto an said axis? Homework Equations Sine Law, Cosine Law The Attempt at a Solution For problem 2/20, the projection onto the b axis was found by multiplying the resultant force by the cosine of 30 degrees. Why does this method...
  49. B

    Static Force Analysis of Linkage

    Hi! I'm trying to complete a static force analysis on the bar linkage shown below. The goal is to find the payload mass in terms of the cylinder forces and everything else in a static environment. To simplify things I've made the assumption that the mass of the payload in the bucket acts at...
  50. K

    Calculating components of a force applied at an angle

    1. The problem statement, all variables, and given/known data Attached is a diagram of what I am trying to solve. I need to calculate the X and Y components for both F1 and F2. The results will then be used in a later problem that I've already solved but I am coming up with an error and I was...
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