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. T

    Statics problem, finding the moment (torque) about a straight line

    1. Determine the magnitude and direction of the moment of the vertical 800 lb force about the straight line through points C and D. (See attachment for diagram) 2. I believe that the equation i need is (Moment vector)=(unit vector)*((position vector)X(Force Vector)) 3. I feel that...
  2. B

    Solve for Tension in Equilibrium: Frictionless Rod with 50lb Load at x=4.5

    Homework Statement This is a question from statics course. Collar A is connected to a 50lb load on a frictionless horizontal rod. Determine magnitude of P to maintain equilibrium when x=4.5. Im confused on the concept of Tension I originally got the answer 11.25 lb like the images...
  3. M

    Engineering statics questions

    Homework Statement Hello everyone, I have a few questions regarding the problem below. 1. I did the process for solving γ correct however I took the 60° angle instead of the 120° angle. The below solution states that γ>90°. Why must is be greater, than 90°, and when would it have been...
  4. M

    Mechanical Linkage Statics Problem

    Hi guys, I've been trying to resolve the following problem but have worked myself into a frenzy and would appreciate some guidance on how to proceed but also to set my mind completely clear. The problem is to find the load torque around the fixed pin joint arising from the piston force F_p...
  5. J

    How do I determine the force in each member of the truss?

    Homework Statement Assume that each member of the truss is made of steel having a mass per length of 4 kg/m. Set p=0 , determine the force in each member, and indicate if the members are in tension or compression. Neglect the weight of the gusset plates and assume each joint is a pin...
  6. J

    Statics Problem Help | Get Expert Assistance Now

    I have to do this problem for my statics class and I don't really understand I will really appreciate, if someone can help me. http://img834.imageshack.us/img834/9360/vn27.jpg
  7. Y

    How does friction affect tension in a statics problem involving belt friction?

    Homework Statement Homework Equations T1/T2=eμs*β where T2 is the larger tension and β is the angle between the tensions.The Attempt at a Solution Isolating each pipe: W1 = 50*9.81 = 490.5N For pipe B, β = (2π)/3 For pipe C, β = π/3 For pipe B, T2 = 490.5N, so I have: 490.5/T =...
  8. Y

    Statics: Shear and bending moment, distributed load

    Homework Statement Homework Equations ƩFy=0 ƩM=0 The Attempt at a Solution Finding the reaction at A: ƩFy=0: A + (L*w0)/6 - (L*w0)/2 = 0 A = (L*w0)/3 ƩMA=0: MA - [(L*w0)/2]*(L/3) + [(L*w0)/6]*((2L)/3) = 0 MA = (w0*L2)/18 For the shear and bending moment: ƩFy=0: (L*w0)/3 - (x*w0)/2 +...
  9. Y

    Statics: Forces in a truss, method of joints

    Homework Statement Using the method of joints, determine the force in each member of the truss shown. State whether each member is in tension or compression. Homework Equations ƩFx=0 ƩFy=0 ƩM=0 The Attempt at a Solution I got the forces at C and D by using the equilibrium...
  10. N

    Ladder with 2 forces of friction and a person climbing (statics)

    1. Homework Statement A uniform ladder of mass m and length L rests against the wall as shown. The wall is frictionless. The coefficient of static friction between the floor and the ladder is μ. The ladder makes the angle θ with the wall. How far along the ladder can a person of mass m...
  11. Y

    What is the Correct Value of Dx in Frame Analysis?

    Homework Statement Homework Equations ƩFx=0 ƩFy=0 ƩM=0 The Attempt at a Solution For the entire frame: ƩMA = 0: -360*15 -240*33 + E*12 = 0 E = 1110 lb → ƩFx = 0: 1110 - Ax = 0 Ax = 1110 lb ← These are the correct values so far. Member BC: By = (4/3)*Bx ƩMC=0...
  12. Y

    What is the Centroid of a Wire and How to Calculate It Using Geometry?

    Homework Statement Homework Equations ƩxiLi=0 The Attempt at a Solution Using geometry to find the lengths and rotating so AB is horizontal, I have: ƩxiLi=0: [((64/80)*L)/2]*L + (-64/2)*80 + (-14/2)*100 = 0 L = 90.28mm
  13. N

    Ladder problem (statics) with 2 sources of friction

    Homework Statement A uniform ladder of mass m and length L rests against the wall as shown. The coefficients of static friction between the floor and the ladder and between the wall and the ladder are equal to each other (μ). What is the maximum value of angle θ that the ladder can make with...
  14. Y

    Statics: Internal forces at a point along a beam

    Homework Statement Homework Equations ƩFx=0 ƩFy=0 ƩM=0 The Attempt at a Solution FBD of the entire thing: ƩMB = 780(0.3) + (5/13)T*(0.72) - (12/13)T*(0.6) = 0 T = 845N ƩFx = Bx + (5/13)*845 = 0 Bx = 325N ← ƩFy = By + (12/13)*845 = 0 By = 780N ↓ Now here is where I...
  15. R

    Finding Equilibrium Forces in a Two-Member Frame

    Homework Statement The two-member frame (see picture attached) supports the 200-lb cylinder and 500 lb–ft couple moment. Determine the force of the roller at B on member AC and the horizontal and vertical components of force which the pin at C exerts on member CB and the pin at A exerts...
  16. Y

    Statics problem, trailer and truck system

    Homework Statement Homework Equations ƩFx=0 ƩFy=0 ƩM=0 The Attempt at a Solution I will call the tire forces A (for the trailer), and B and C (for the truck) I got the correct answer for A by isolating the trailer and writing this equation for it: ƩMD = 2400*9 - 2*A*11 = 0...
  17. Y

    Statics problem, analysis of a frame

    Homework Statement Homework Equations ƩF_y=0 ƩF_x=0 ƩM=0 The Attempt at a Solution The weight of the wire is 500*16=8000lb I isolated each part of the system: Using a force triangle on the cross section of the wire, knowing it is a 345 triangle: 8000/4=B/3=D/5 B=6...
  18. R

    Statics: Forces in Cartesian Vector form

    Homework Statement For cable AD it is known that the magnitude is 14 kips, x-component has a value of -6.216, the direction angle in the z-direction is 83.63°, and Fy is less than zero. Find forces in Cartesian vector form, coordinates of point D if it lies on the x-z plane and point A is (0...
  19. S

    Statics Question with Couple Moments and Right Hand Rule Comprehension

    Homework Statement I'm having problems with understanding how to use the right hand rule as it applies to forces and determining moments. If I understand correctly, The fingers point in the direction of the force, then curl in the direction of r, but I'm not sure what r would be in this...
  20. Y

    What is the tension in the cable and the reaction at D?

    Homework Statement A force P of magnitude 90 lb is applied to member ACE, which is supported by a frictionless pin at D and by the cable ABE. Since the cable passes over a small pulley at B, the tension may be assumed to be the same in portions AB and BE of the cable. For the case when a = 3...
  21. P

    Statics problem: cats on a beam, tension of cables calculation

    Homework Statement A 30 kg neon sign is suspended by two cables, as shown. Three neighborhood cats (5.0 kg each) find the sign a comfortable place. Calculate the tension in each cable when the cats are in the positions shown...
  22. Y

    Statics Problem, Moment About an Axis

    Homework Statement Problem 3.60: Homework Equations M_{AD}= \begin{vmatrix} \lambda_x & \lambda_y & \lambda_z \\ x_{B/A} & y_{B/A} & z_{B/A} \\ F_x & F_y & F_z & \end{vmatrix} The Attempt at a Solution Looking at the figure, these are the unit vector components...
  23. R

    Statics- Resultant couple moment

    Homework Statement If F_1 = 100N , F_2 = 120N and F_3 = 80N , determine the magnitude and coordinate direction angles of the resultant couple moment. Homework Equations M=Fd M=r x F MR=Ʃ(r x F) The Attempt at a Solution I found the couple moment for each force: M1=F1d=100(0.2) or...
  24. S

    Understanding Electrostatic Induction in Dielectrics

    During electrostatic induction,a posivitiely charged body is brought near to a uncharged body.During this uncharged body gets bound negative change toward the end of the body near to charged body. My question is in reality what happens to the electron and proton of uncharged body.Do the all...
  25. F

    Statics Engineering Problem Involving Beams

    Homework Statement Here is a flicker link. http://www.flickr.com/photos/93763273@N05/8750975006/sizes/l/in/photostream/ Homework Equations The Attempt at a Solution Here is the link to my solutions...
  26. M

    Understanding Normal and Gravity Forces in Stacked Block Structures

    why is it when you stack two blocks on each other that the top box with mass M_t has a normal force of M_t and a gravity force M_t*gwhere as the bottom box has a normal force of M_t+M_b where M_b is the mass of the bottom box yet gravity is M_b*g? i guess i don't get why gravity is the same...
  27. J

    Engineering Statics (Equilibrium of Rigid Bodies)

    I have problems understanding the sense of reactive forces generated at pins / connections. Book is by Hibbler, I am posting links to images which will better explain my questions. The following links are concerning reactive forces. 1# http://i.imgur.com/0x62lp2.png 2#...
  28. J

    Statics, centroids of lines, areas and volumes

    Hi to everybody. I´m reading a book about statics and I cannot understand this chapter. I have been calculating moments of forces in hundreds of problems, when I found a force acting on a body I needed to fix a coordinate system, then calculating the moment arms of that force around a point...
  29. C

    Statics: Drawing Shear and Moment Diagram

    http://img687.imageshack.us/img687/5889/shear.png I'm having trouble drawing the shear diagram on MAsteringEngineering. I'm pretty sure the values are correct too? I got By = 10.5 and Ay = 9.5 V(x) = -2x+9.5 for the distributed load so when I set V=0, I find the x intercept to be...
  30. G

    Statics problem - too many unknowns?

    Homework Statement See attachment. Find the tension in the string that is keeping this weird contraption together. The left stick has mass m, the right stick has mass 2m. m, θ and L are known quantities. Homework Equations The Attempt at a Solution Tried starting with the right...
  31. J

    Statics, compute force in member of a frame

    Statics, compute force in member of a frame [SOLVED] Hi guys, I opened this thread but then I saw the mistake and I tried to delete it but I don´t know how, I´m sorry. Homework Statement I´ll show the problem using a picture: Homework Equations Sum forces = 0 Sum moments = 0 M = r x f...
  32. E

    Maximum Capacity of a Flat-Bottomed Rowboat

    Homework Statement A rectangular, flat-bottomed rowboat has a mass of 120 kg when empty. It's 3 meters long, 1 meter wide, and .24 meters deep. How many 85 kg people could it hold before swamping? Homework Equations d=m/v ? The Attempt at a Solution I need to determine the...
  33. J

    Statics, forces in each memeber of a truss

    Homework Statement I´ll show the problem using a picture: Homework Equations Sum Forces = 0 Sum Moments = 0 The Attempt at a Solution Well, I´m a bit confused because I need to take care of the weight of the own structure. 1.- First attempt to solve to problem, since the structure is...
  34. J

    Statics Table Homework: Equilibrium & Free Body Diagrams Explained

    Homework Statement Homework Equations Free Body Diagrams, Moments, Equilibrium The Attempt at a Solution Started off by giving x,y,z coordinates to the 4 points (A,B,C,E). E is the centre of the table and I used that as my origin. A=(-1.034, 0, -0.6) [Leg to the Left)...
  35. J

    How does this statics design FBD look?

    I have a FBD I'm not quite sure about. I attached what i have along with the original picture. 2 pin supports plus the other one on the hydraulic jack. How does it look? Here's my problem: The chute of a concrete truck for delivering wet concrete to a construction site is shown. The length of...
  36. J

    Statics, forces in each memeber of a truss

    Homework Statement I´ll show the problem with a picture: Homework Equations Sum forces = 0 ; The Attempt at a Solution Well I tried to solve the forces equations at the joint D, but I see three unkown quantities ED, BD and CD, and I have two equations, one for the X axis, and...
  37. J

    Physics IA, Statics, and Cal III in the fall - doable?

    My adviser has suggested this lineup for me for the fall semester this year. I have not had any problems understanding calculus so far, and I am very excited about physics and statics, but the idea of this kind of workload is new to me and is quite daunting. Is this doable? Or would you advise...
  38. C

    Statics: Rigid Body Equilibrium

    Hello, I was wondering if someone could explain part of the solution to this problem for me. http://img706.imageshack.us/img706/5517/disksproblem.png To the right is the Free Body Diagram of Disk E, and I can draw the forces on there well enough. But I really do not understand how they...
  39. A

    Zero-force member problem (Statics)

    Homework Statement Determine the zero force members in the following truss Homework Equations - If only two members meet in an unloaded joint, both are zero-force members. - If three members meet in an unloaded joint of which two are in a direct line with one another, then the third...
  40. J

    18 Free body diagrams, statics

    Hi to everybody Homework Statement Well I need to identify the forces acting on the bodies using free body diagramas, it´s not necessary to calculate anything, it´s only to learn about free body diagrams. I will write my thoughts about the FBD and I will appreciate a lot if you see that I´m...
  41. J

    Statics, determine the force required to rotate a body

    Homework Statement I´ll use a picture to show the problem: Homework Equations Sum forces=0 Sum Moments=0The Attempt at a Solution Basically I´m not sure about the forces on the free body diagram and I´d like to talk about them. Assuming that P is not acting, and the body is masless...
  42. C

    Statics: Find resultant force and couple moment

    http://imageshack.us/a/img842/2497/112639506.jpg Calculate the resultant force’s magnitude and the couple moment. Let a = 3.70 m w1=5.35kN/m w2=4.00kN/m The resultant force of the triangle is 1/2(3.70)(5.35)=9.898 kN The resultant force of the rectangle is (4)(3.70) = 14.8kN So...
  43. C

    Statics Problem istributed Loads

    Statics Problem:Distributed Loads http://imageshack.us/a/img845/5825/112639502.jpg When measuring from the left side of the beam Xa,Xb ,Xc ,Xd ,Xe ,and Xf are the locations where the resultant force is applied in each of the six cases. Rank these six locations. Rank the items from...
  44. J

    Statics Springs Design Problem

    Statics Springs "Design Problem" Homework Statement Here's a problem I've been very determined to figure out, but I can't. I attached the picture. This single problem is 5% of my grade, so I'd appreciate any help! A plate storage system for a self-serve salad bar in a restaurant is shown. As...
  45. J

    Statics, beam attached to a wall, reaction forces

    Homework Statement I´ll show it with a picture: Homework Equations Static equilibrium, Sum Forces=0 ; Sum Moments= 0 The Attempt at a Solution With the Fx, and Fy equations I can calculate the reactions Rx and Ry but I don´t understand the moments equation: Sum M around...
  46. J

    Statics, bike on inclined plane

    Homework Statement I´ll need an image to show the problem: A bike with length L is on an inclined plane, the distance between the center of gravity and center wheel centers A,B is L/2. Brakes are acting on the wheels so we have a static position. In the picture is possible to...
  47. A

    Best Statics Textbook? Help Finding Right Book

    Please help! I'm having trouble in Statics, and my textbook isn't helping. I've got Vector Mechanics for Engineers by Beer and Johnson. I've heard it's supposed to be a good text, but am finding it inscrutable for some reason. Any recommendations?
  48. C

    Statics Question: Finding Resultant Moment

    http://img831.imageshack.us/img831/8005/f48am.jpg Determine the magnitude of the resultant moment produced by the forces about point O Determine the direction of the resultant moment produced by the forces about point O I first break the forces down to their components. F1x =...
  49. C

    Basic Statics problem, forces on a Truss

    Homework Statement The truss is supported by a pin at A and roller at B. Determine the support reactions. Homework Equations sum of forces along y-axis, sum of forces along x-axis, sum of all torques The Attempt at a Solution Sum of x= Fax+ Fbx+ 5sin45=0 Sum of...
  50. J

    Problems about statics. Force and Moment calculations.

    Homework Statement I´ll use an image to show the problem that you can see as attached file. I need to calculate a force-couple system applied to the point C in red, equal to the force f0 applied to the point E. Homework Equations M=fd The Attempt at a Solution Well in these...
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