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. M

    Statics project: where to place a support

    Homework Statement I have a project for my statics class. My topic is equilibrium of a rigid body, and I am building an assembly that will have four different support reactions. They will all be attached to one central post for ease of construction, but they will be analyzed as separate...
  2. Femme_physics

    Statics problem - is the mistake mine or the solution manual?

    So I got everything right other than Rd (the end). I personally think there's a mistake in the solution manual. Homework Statement Basically these are all pin joints, even the "hydrolic cylinder" (CD) is weightless and connected by pin joints, so the fact it's called or drawn as...
  3. Femme_physics

    Statics, crankshaft-like device. Need help.

    Homework Statement http://img841.imageshack.us/img841/4725/device01.jpg (I hope I translated it correctly, this has some technical terms...) This device is used as a key for installing a disk on a stational shaft, O. The device is equipped with pins A and B, that goes into the holes of the...
  4. Femme_physics

    Statics, moment of inertia simple square-shape (no calculus)

    Statics, moment of inertia simple square-shape...need help (no calculus) Homework Statement Calculate the moment of inertia to the central axes Xc and Yc for the sketched cross-section. Xc = 33.9 mm Yc = 150 mm http://img822.imageshack.us/img822/1303/97823499.jpg Uploaded with...
  5. Femme_physics

    Statics - It seems simple, but there must be a catch

    Statics - It seems simple, but there must be a catch... (Sorry if I'm overasking for one day. Clearly I'm doing a marathon of statics exercises today and you're all super helpful ^^) Homework Statement This structure is made out of 2 weightless parts, BCD and AC, connected by joints. At...
  6. Femme_physics

    Statics - When 2 unknowns and 2 equations cancel each other out

    I hate it when that happens, but whenever I make 2 equations and 2 unknowns, setting the sum of all torques at the known force (rather than the support) and do sum of all forces equation (either of x or y) I get complete canceling of terms and 0 = 0. What does it mean...
  7. Femme_physics

    Statics - Confusion about forces direction

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  8. P

    A Flexible chain between two hooks (statics)

    Homework Statement A flexible chain weighing 41.0 N hangs between two hooks located at the same height. At each hook, the tangent to the chain makes an angle θ = 41.5° with the horizontal. (a) Find the magnitude of the force each hook exerts on the chain. (b) Find the tension in the chain at...
  9. P

    Statics question - Method of joints

    The problem is attached. I have to solve for the force in the member BC. The thing I need help with is solving for the two attachments. I already broke it down into the forces and directions, but what do I do with the lower attachment? How do I find the x displacement of point G from E if I'm...
  10. T

    Electro Statics What am I missing?

    Electro Statics...What am I missing!? Homework Statement A balloon rubbed against denim gains a charge of 8.0microcoulumbs (I can't do the sign O.o). What is the electric force between the denim and balloon when the two are separated by a distance of 5.0 cm? Homework Equations...
  11. M

    Solve Smallest Value of Ms for Ladder Equilibrium

    So there is a ladder leaning against the wall. its a 2.5 (base), 6 (height), 6.5 (hyp) triangle. the coefficient of static friction is zero at B (corner of 6 & 6.5). we need to determine the smallest value of Ms at A (corner of 2.5 & 6.5) for which equilibrium will be maintained. They do not...
  12. D

    Statics question: when do I need to find the support reactions?

    I didn't use the format because my question is more general. I want to be able to understand the logic so I can apply it where appropriate. We're finding forces (and whether they're in tension or compression) using the Method of Joints and Method of Sections. I don't understand why...
  13. I

    Statics - Centroid of a 2-D figure

    Homework Statement Problem Homework EquationsArea of a semi-circle, area of a semi-sector of a circle, centroid of a semi-circle, centroid of a sector, general equation for centroid of a plate: (X-Bar) * \SigmaArea = \Sigma(x-bar * Area) The Attempt at a SolutionAttempt. I tried my...
  14. L

    Statics: forces on a beam and reactions

    Homework Statement a horizontal beam has a pin at 0m(point A), a 90N (-90i) force at .2m(point B), a pin at .4m(point C) and a 180N (-127.3i + -127.3j)at (45 degrees) force at .6m(point D). the pin at point A is attached to a vertical wall with rollers, the pin at point C can't move. The beam...
  15. J

    Statics, Stress, and Machine design

    Homework Statement I have attached a copy of the assignment problem. I have been having serious trouble finding the value of the force P. I know the equations to use for part b and c but I need to know the force P to complete the rest of the problem.Homework Equations a) The problem tells me...
  16. M

    What is the solution to this waves/statics problem?

    Homework Statement [PLAIN]http://img5.imageshack.us/img5/7653/73215327.jpg The answer in the text is sqrt(15)Mg I am not sure how to obtain this from. Please advise.
  17. J

    Statics (frictional force) problem

    Homework Statement The question is: A uniform ladder of mass of 50kg is palced with its foot on a horizontal floor and its top against a vertical wall. Determine the minimum value of themass which must be placed against the foot of the ladder to retain it at an angle of 45degrees to the...
  18. C

    Forces in Truss Members (Statics)

    Homework Statement See attachment. Edit: Point A is a pinned connection (has a reactionary force in X and Y direction). Point B is a roller connection (only has reactionary force in Y direction) Homework Equations Sum Fx=0 Sum Fy=0 Sum of Moments=0 The Attempt at a Solution...
  19. K

    Resolving Forces in 3D - Statics

    1. Three guy wires hold a pole BO as shown. The resultant R of the forces due to the three wires has a magnitude of 1000-N and is directed on the pole BO. Force F2 and F3 have a magnitude of 400-N and 500-N, respectively. The distance from point A to point D is 5-m. Find the tension in cable...
  20. P

    How to Find the Projection of a Force Along the Y-Axis in 3D?

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  21. Femme_physics

    Statics is this problem easy or hard?

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  22. Femme_physics

    Calculating Forces at Supports A and D for a Hard Frame: Step-by-Step Guide

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  23. Femme_physics

    Questions about statics, mechanics, pulleys

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  24. A

    Why is the weight going upward? Statics

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  25. K

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  26. W

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  27. F

    Statics Problem: Crane with Suspended Ball | Help & Solutions | Mechanics

    Homework Statement Hello :) I am stuck on this mechanics problem. Any help would be hugely appreciated, because I am just starting with statics. Thank you in advance . A diagram of the problem can be found here :http:////img97.imageshack.us/i/79504950.png A small crane is used in demolition...
  28. M

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  29. W

    Statics Question - Method of Sections

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  30. I

    Finding Tension in a Rod Attached to Sliding Blocks

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  31. M

    Possibility of taking Dynamics, Thermo, and Statics simultaneously?

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  32. S

    Statics - Distributed Load Over Beam

    Hello, I am attempting a problem in an older statics textbook an image of which is attached. No matter what I try, I get a solution of between 0.52 and 0.53 metres and was hoping someone could verify if the textbook answer of 0.48m is right or wrong. Thanks Heaps, Scott.
  33. G

    Is it Possible to Have Statics in Captured Video?

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  34. T

    Solving Simple Statics Problem - Find Force Fb & Fa

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  35. L

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  36. P

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  37. H

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  38. I

    Statics/ equilibrium - angle question

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  39. S

    Resources for Engineering Statics? (1st year course)

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  40. Y

    General Statics Question-Frames

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  41. T

    Statics ladder and friction less wall question

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  42. M

    Design 3 Cable System for 25m Radio Tower: R, Diam of Steel Cables

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  43. Y

    Statics Equilibrium Problem - 3 Force body in equilibrium

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  44. F

    What is Solving a Statics Problem: Finding the Resultant Force?

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  45. B

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  46. B

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  47. C

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  48. D

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  49. I

    Basic Statics problem with scalar components and force

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  50. R

    Solve 4 Unknowns: Statics Question

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