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. C

    Statics Question: Finding resultant force and orientation

    Determine the magnitude of the resultant force FR. Assume that F1 = 230 and F2 = 395 Express your answer to three significant figures and include the appropriate units. Determine the direction of the resultant force FR , measured counterclockwise from the positive x axis. I got the...
  2. S

    Statics of hangman beam / guitar neck under load

    Hello all, I am trying to understand what the relationship is between the length or height h of a guitar neck and how far in the x direction it is displaced (δ) given the same tension in the strings and width of the neck, and assuming the neck is anchored and rigid at the guitar's body. Is it...
  3. B

    Statics Problem, Engine Boom

    The 6575-lb engine is suspended from the crane boom. Assume the initial weight of members CD and AB to be 10lb/ft and 50lb/ft. Determine the resultant internal loadings acting on the cross section of the boom at point E. Also, find the joint reactions at A, C and D. So far I solve for the...
  4. Astronuc

    Engineering Mechanics: Statics & Dynamics by Russell Hibbeler

    Author: Russell C. Hibbeler Title: Engineering Mechanics: Statics & Dynamics Amazon Link: https://www.amazon.com/dp/0132915480/?tag=pfamazon01-20 Prerequisities: Prior or concurrent experience in Calculus, Introductory Physics Level: Undergraduate Table of Contents: 1 General...
  5. H

    "Statics of Rigid Bodies: 2 Questions

    2 Questions about statics of rigid bodies Homework Statement A cable of length 8.5 m is attached to the two posts as shown in Fig. 6. The crate has a mass of 1000 kg. Find the x and y components of the forces exerted by the cable on the eyebolts and find the tension force in the cable. The...
  6. B

    Statics problem. Is my work correct?

    Homework Statement Homework Equations ƩF=0 ƩM=0 The Attempt at a Solution I have done parts 1-3 (parts 1-2 in image) and I think it's right. It's been a while since I've had statics and I'm not 100% sure it's right. For part 4, where the pulley meets the frame at F do I need a...
  7. J

    What is the correct component force along the axis of the hook?

    I worked out the attached problem. I was just looking for a logic check on my work. The problem asks you to find the component force along the axis of the hook. Thanks
  8. A

    Equilibrium and Statics involving a mass attached to three strings

    Homework Statement Find the forces of the three strings of this image. http://www.flickr.com/photos/79276401@N05/8395815988/in/photostream Homework Equations Using gravitational constant to find force of the mass. Using algebra to find the forces of the three strings. The Attempt at a...
  9. H

    Statics: Bending of a beam/evenly distributed force problem

    Hello, and sorry for my English, as I am Norwegian. I have a statics problem which I can not understand. I've taken a pic from my book: The problem asks me to find the largest bending stress, σb, in the incisions 1 and 2. I have the solution in front of me, I just don't understand...
  10. O

    Solve Statics Problem: Find Theta Angle Balance

    I basically have to solve the system below for which angle theta it's in balance. Meaning all forces equal out to 0. The answer is in terms of the variables. It's been a while since I've done statics like this but it has come back to bite me in the *** again. I started out by moments...
  11. P

    Engineering Mechanics - Statics

    Can one obtain a negative value for mobility i when working out the mobility of a structure; the structure being constrained by either pins, sliders or fixed points? What happens with a negative mobility?
  12. H

    Problems of statics, angular motion and simple harmonic motion

    All Questions are shown on pictures. My Calculated answers: A1(a) R= 19.21∠68.7o N (b) E = 19.21∠-111.34o N or = -19.21∠68.7o N <--- Is't either one answer is correct or not? If not, which answer is correct and why? Thanks. A2(b) I = 0.5mr2 = 1.125kgm2 A2(a) k=(I/m)1/2 = 0.212m...
  13. E

    Fluid Statics - Forces on Submerged Surface?

    QUESTION Rainwater collects behind the concrete retaining wall shown in the figure. If the water saturated soil (specific gravity 2.2) acts as a fluid, determine the force and center of pressure on a 1-m width of the wall. PROBLEM 1. What does it mean by 1-m width of the wall? Is it 1-m...
  14. L

    Engineering Statics Equilibrium

    hi, for question two on the attached pdf, how would the equilibrium in the x work? From what i understand there must be an x and y component for the pin support at A because it acts at an angle but the support at B only has a y component because it is a rocker.
  15. W

    Best Way to Solve Statics Problems

    My question is very simple. When solving static equilibrium problems (such as finding reactions at joints) when should I take the moment about the x,y, and z axes and when is it better to take a joint and find the reaction forces on that joint? Also any other tips will be appreciated.
  16. L

    What Friction Coefficient is Required for Outward Sliding at Points A and C?

    Homework Statement The unstretched length of a spring is 1.5 ft. What friction coefficient,μ, at A and C is needed so that P=500 lb would tend towards points A and C sliding outward? Given spring constant k=70 lb/ft Diagram- Inverted triangle such that height is 4 ft to point B. Force P...
  17. T

    Statics: Balancing beam of unknown length

    Homework Statement A horizontal meter stick has a mass of 217 g. Three weights ride on the meter stick: 265 g at 40.7 cm, 191 g at 75.9 cm, and 195 g at 99.3 cm. At what location on the meter stick would the system be in balance if it were suspended there?Homework Equations ƩF=0 Ʃτ=0 Center...
  18. E

    Weird Statics Truss Problem - Finding reactions

    So I'm looking for the reaction forces at the left end of the truss before I solve for the forces in the members of the truss in terms of F and theta. I summed forces in the x, y direction, took moments about point A,B, to get 4 equations in 4 unknowns (Ax, Ay, Bx, By). However, although Ax,Bx...
  19. A

    How to Calculate Forces in a Beam Using the Method of Sections

    IHi guys with part b of this question I am having trouble. I have cut it it at the specified members and used the top half. Now i take the moment at A to get the force in BC. (CW+)M@A=(6*3)+(6cos(30)*3)=0, But when you solve this it doesn't give you the answer its supposed to be, I am probably...
  20. A

    Fluid Statics (multiple choice question)

    Homework Statement #1 If you hold a block of lead and an identical size block of Styrofoam under water, the buoyant force will a) be greater on the lead block. b) be greater on the Styrofoam block. c) be the same on both blocks. d) depend on the depth that each block is held. #2 Salt...
  21. A

    Calculating Support Forces in Statics: Solving Equations for A and B

    I've been trying to figure this out for 4 days now. I'm completely stumped. I've attached a picture of the diagram: http://postimage.org/image/t3d5i0l1v/ I found the force in F: F = 25.04 lb ---> 16.92i + 18.46j Now I need to find the support forces at A and B. I'm not sure if this is right...
  22. V

    Statics: A pulley system in equilibrium

    Homework Statement Hi, I am confused by this physics question and I was wondering if someone could help me out. I have a system with 2 pulleys and 3 weights. They are all held together by one string, the two weights on the outside of the two pulleys, both weighing the same, hold up the...
  23. M

    Statics of Particle homework help

    Homework Statement In the following diagram (see attachment), w=80N and the net force is 0. The Attempt at a Solution I basically made two free body diagrams and applied Net Force = 0 for each axis, obtaining 4 equations with 4 variables (T1,T2,T3,T4). I got T1=56N T2=98N T3=115N...
  24. Y

    Calculating Center of Mass: Xi &amp; Yi for Statics

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  25. I

    Calculating Force on Peg in Uniform Ladder Against Wall | Quick Statics Question

    Homework Statement A uniform ladder is 10m long and weighs 400 N. It rests with its upper end against a frictionless vertical wall. Its lower end rests on the ground and is prevented from slipping by a peg driven into the ground. The ladder makes a 30◦ angle with the horizontal. The...
  26. S

    Statics Truss Problem Involving Method of Sections

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  27. P

    Structural Mechanics - Statics / Truss

    Homework Statement The simply supported timber foot bridge shown in figure 5 spans 7 metres and, as shown, is carried by two Engineering grade Douglas Fir beams. The uniformly distributed load due to the self weight of the foot bridge and beams is 96 kg/m. The bridge is required to carry a...
  28. K

    Statics Questions involving finding forces

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  29. K

    Working out support reaction of a frame - Statics

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  30. H

    Statics question involving moments and cranes

    Homework Statement The crane below is on level ground. The x-axis is through the contact points of the rearmost wheels with the ground, the y-axis is parallel to the front-to-back centerline, and the z axis is vertical as shown. The bed (platform) of the crane is 3 ft above the ground. For...
  31. H

    Statics question about moments

    Homework Statement Find the components of the force at D and C using moments picture attached Homework Equations M=F x r The Attempt at a Solution I'm really stuck on this one. The force from the 70 kg weight is 70*9.8 = 686N, so F=-686j. I found the moment about point C...
  32. J

    Solving Mechanics Statics Homework Problem

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  33. U

    Edexcel Physics Statics Homework

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  34. B

    Solving 3D Statics Problem with 800N Lamp

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  35. S

    Statics Question / Understanding Direction

    Homework Statement I'm trying to understand how to determine the sign (+/-) of a given couple. In the sample problem below it shows the 30 lb couple (on the zy-plane) having a negative value for it's force. Is this found by using the RHR? And if so, in which direction do I orient my hand? In...
  36. D

    Statics Forces Problem (Trusses)

    Homework Statement I was doing a problem with my friend (the image that is attached to this) and when looking up a solution online... It said that the forces at reaction supports B and C are 5 kN in the y direction... Homework Equations The Attempt at a Solution We thought...
  37. Q

    Statics Questions: Help with Finding Correct Answers

    The first picture is the question picture. The second picture is my calculation for this questions. I can't find the correct answer, everybody know why? Thanks
  38. D

    Why Does This Statics Problem Not Specify Resultant Force Direction?

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  39. M

    Statics - Show a massless stick feels forces along the stick

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  40. J

    Statics Equilibrium: Normal Force and Static Friction

    1. The homogeneous square body is positioned as shown. If the coefficient of static friction at B is 0.40, determine the critical value of the angle theta below which slipping will occur. Neglect friction at A. The image: 2. NA is the Normal force at A, which is perpindicular to the...
  41. H

    Solving Statics Questions with Different Units

    The units are different. One is the force unit, and one is the length unit. Then how to find the h? Question is attached in the file thanks
  42. U

    Free-Body Diagram for Statics of a Crane

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  43. H

    Learn How to Solve Basic Statics Problems with Expert Guidance

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  44. D

    Statics. Equilibrium With Springs and Tension Question.

    Homework Statement The springs BA and BC each have a stiffness of 500N/m and an unstretched length of 3m. Determine the displacement d of the cord from the wall when a force F = 175N is applied to the cord. Homework Equations F=ks ƩFx=0 ƩFy=0 The Attempt at a Solution This is as...
  45. R

    Solving for Coordinate Angles in Statics Question

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  46. R

    Solving Statics Problems: Setting Free Body Diagrams to Zero

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  47. N

    How Do You Calculate the Moment about a Point in Statics?

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  48. N

    Name of equilibrium when ∑Fx and Fy = 0 but there's still a moment (statics)

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  49. C

    Statics 221. Determine moment.

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  50. C

    Having a difficult time in statics. (EM 221)

    A 21-pound force is applied to the control rod AB as shown. Knowing that the length of the rod is 9 in. and that α=25°, determine the moment of the force about point B by resolving the force into horizontal and vertical components. I wish I could say I have some work to show progress, but I...
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