What is Static equilibrium: Definition and 357 Discussions

In classical mechanics, a particle is in mechanical equilibrium if the net force on that particle is zero. By extension, a physical system made up of many parts is in mechanical equilibrium if the net force on each of its individual parts is zero.In addition to defining mechanical equilibrium in terms of force, there are many alternative definitions for mechanical equilibrium which are all mathematically equivalent. In terms of momentum, a system is in equilibrium if the momentum of its parts is all constant. In terms of velocity, the system is in equilibrium if velocity is constant. In a rotational mechanical equilibrium the angular momentum of the object is conserved and the net torque is zero. More generally in conservative systems, equilibrium is established at a point in configuration space where the gradient of the potential energy with respect to the generalized coordinates is zero.
If a particle in equilibrium has zero velocity, that particle is in static equilibrium. Since all particles in equilibrium have constant velocity, it is always possible to find an inertial reference frame in which the particle is stationary with respect to the frame.

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  1. E

    Unhinged -- Static Equilibrium for a Door

    Homework Statement Homework Equations Torque = r x F The Attempt at a Solution I expect the door to fall.
  2. M

    Calculating force to tip over a cabinet (static equilibrium)

    Homework Statement Homework Equations How do you solve for the force in this problem and also the coefficient of static friction and minimum force to tip the cabinet over if the point of application can be chosen anywhere on the cabinet? The Attempt at a Solution I tried setting up tables...
  3. A

    Spring angles at static equilibrium on application of force

    Homework Statement Two linear springs with stiffness Kh, Kv are attached to a single mass m at right angle to each other, i.e; one of the spring(Kh) is in the horizontal direction(x-axis) and the other(Kv) is in the vertical direction(y-axis). A constant force F is being applied to the mass...
  4. U

    Lifting a Beam with a uniform weight distribution

    Homework Statement Hi There, I'm having trouble understanding (what I guess should be) a simple concept and so I can't apply it to a project I'm working on (also kind of rusty on torques and mechanics problems) If I have a hinged beam (of uniform weight) and I lift it from one end and stay...
  5. M

    MHB Uniform rods and disk in static equilibrium

    i am stuck on question 9 can anyone help me out. thanks
  6. person123

    Exploring Pulley System Equilibrium: Solving for y when x Changes

    I was working on a pulley system as shown here: The mass on the right and left side is equivalent, and I am solving for when the system is in static equilibrium. Theta is the angle between the rope on either side of one of the pulleys. H and y are both measured from the original position of...
  7. 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...
  8. J

    Static Equilibrium: Understanding Changes in Tension and Vertical Force

    Homework Statement If the load on the uniform beam shown below is moved to the left, how do the tension force T and the magnitude of the vertical force Fv exerted by the wall on the hinge change? The answer is A Homework Equations torque = Fdsin(theta) The Attempt at a Solution My equation...
  9. Kevin de Oliveira

    Static Equilibrium: Why Does Changing Pulley Position Affect Relative Angles?

    I have a 3 pulley system statically balanced hanging weights at a determined relative angle (we are taking into account friction). If I change the position of one pulley, angles will remain the same. However, if I have a 4 pulley system, at the same conditions, changing one's position will...
  10. R

    Static equilibrium with friction question

    Homework Statement This is a real world application. I am posting it here to follow the guideline for any "coursework-like" questions, but since I have no formal training, I'm not sure what category this would actually fall under. Any recommendations for a more specific posting location would...
  11. D

    Direction of force exerted by ground for the ladder problem

    This question pertains to the classic ladder-leaning-against frictionless wall scenario. The system is in static equilibrium. The ladder is thin and can be assumed to be made of a homogeneous material so that the center-of-mass lies at the geometric center. The forces in this scenario is...
  12. E

    Static Equilibrium - Ladder problem with a twist.

    Homework Statement A board that is of length L = 6.0 m and weight W = 335.7 N rests on the ground and against a frictionless contact at the top of a wall of height h = 2 m (see figure). The board does not move for any value of greater than or equal to 65 degrees but slides along the floor if...
  13. kamhogo

    What is the force exerted by each hinge on the door?

    1. Homework Statement The door has a mass of 30 kg, is 200 cm long and 90 cm wide. The hinges are installed at 25 cm from the bottom (R2) and 25 cm from the top (R1). What are is the magnitude of the force exerted by each hinge on the door? The door is in a state of static equilibrium...
  14. merricksdad

    Determining mass of a weight on a three spring scale setup

    Homework Statement Given three spring scale readings, positioned at unknown angles, find the mass of the weight hanging from all three scales without using trig, and without measuring the angles. You have only a yard stick. This is a static equilibrium problem. Homework Equations Not allowed...
  15. M

    Solve Static Equilibrium: Beam, 520N Force, Cable Tension

    Homework Statement A uniform vertical beam of mass 40kg is acted on by a horizontal force of 520N at its top and is held, in the vertical position, by a cable as shown. a) Draw a free body diagram for the beam, clearly labelling all the forces acting on it b) Calculate the tension in the cable...
  16. E

    I Proportion in 2D and 3D static equilibrium?

    If you were to look at a simple 2D or 3D static equilibrium diagram, where a mass is suspended by multiple ropes at different angles, my gut feeling is that there is a fairly simple proportion between the distance between the center of mass and the rope (the distance created opposite of the...
  17. X

    Static equilibrium: setting up the equation

    Homework Statement A rigid wire frame is formed in a right triangle, and set in a vertical plane as shown. Two beads, of weight W1 = 1.5 N and W2 = 2.5 N, slide without friction on the wires, and are connected by a cord. When the system is in static equilibrium, what is the tension in the...
  18. A

    Static Equilibrium Problem involving Moments

    Equations: Net torque=0=Net force I believe this is a static equilibrium question but can't figure out how to do it
  19. S

    Static Equilibrium Pulley Problem

    Homework Statement The attachment above contains the diagram given in the problem M1 = 25kg M2 = 35kg Friction coefficient between M1 and stucture = 0.15 Friction coefficient between M1 and M2 = 0.25 Friction on pulleys and mass on pulleys is negligible. Find the minimum mass M3 for sliding...
  20. RoboNerd

    Question about static equilibrium

    1. Homework Statement problem is above Homework Equations sum of torques = I * angular acceleration = 0 for rotational equilibrium The Attempt at a Solution OK, here's what I tried to do. I wrote sigma Fy = Fleft pier up + F secondleftpierup - Fg,beam = 0 I assumed that the two piers have...
  21. U

    A simple static equilibrium problem

    Homework Statement Suppose we have a folding ladder, so that when its legs are spread it makes an isosceles triangle. Suppose it has a support that runs parallel to the ground. There is a bucket of paint that rests on top of the ladder, and the mass of the ladder is negligible. Data: The legs...
  22. Dietrichw

    Static equilibrium, tension and compression

    Homework Statement The figure below shows a light truss formed from three struts lying in a plane and joined by three smooth hinge pins at their ends. The truss supports a downward force of = 1 330 N applied at the point B. The truss has negligible weight. The piers at A and C are smooth. The...
  23. STEM_STRUGGLES

    Analyzing Forces in a Diving Board System

    Homework Statement There is a diving board held up by two pillars A and B, and there is a diver standing on it's edge. What are the directions of the forces exerted at points A and B? Picture Below: Homework Equations F_NET = 0 T_NET =0 The Attempt at a Solution I thought both A and B were...
  24. RodriRego

    Finding Static Equilibrium: Solving a Rod and Cable System

    Homework Statement Homework Equations Fr (resultante force) = 0 Sum of all forces aplied at the strut = 0 Sum of the torque of all forces = 0 The Attempt at a Solution I started by analysing the torque, since the strut is on static equilibrium and I ended up having C (tension on the cable)...
  25. S

    Static Equilibrium: holding a sign

    Homework Statement You are holding a sign as shown below. The sign (including the horizontal bar it hangs from) has a mass of 2.20 kg and is 40.5 cm wide. The sign is hanging from a 1.03 m tall, 4.46 kg vertical post. The sign is symmetric with a uniform mass distribution as implied by the...
  26. R

    Are these torques correct for a simple balancing/fulcrum exp

    Homework Statement For my physics lab, they had us do a simple static equilibrium experiment where we rested a ruler on a fulcrum (at its center of mass) and then attached varying amounts of weight on either end at different distances from the fulcrum. This screenshot is the data we recorded...
  27. K

    Angles in a Static Equilibrium

    Homework Statement I have 3 masses (Fα, Fβ & Fg) with 2 pulleys, and a wind variable which is in static equilibrium. I have already calculated the appropriate forces for the 3 masses by multiplying it with 9.81m/s² (gravity). Fwind = 60N Fα = 313.9N Fβ = 619N Fg = 882.9N I'm required to find...
  28. T

    Frequency problem (static equilibrium)

    Homework Statement The lower end of a uniform beam is attached to a vertical wall by a frictionless pivot. The beam extends away from the wall and upward, making a 62° angle with the wall, and it is held in place by a horizontal wire attached from its upper end to the wall. The wire's length...
  29. M

    Static Equilibrium: Solving Homework Questions

    Homework Statement Homework EquationsThe Attempt at a Solution [/B] 8) The mass is in static equilibrium meaning the sum of all the forces acting on it are equal to 0. Both sides are holding have the same tension because they have the same angle. SINΘ = (Opposite) / Hypotenuse = Hypotenuse...
  30. C

    Magnetic Force/Field, Current, Inclined Plane Problem

    Hello! I just need someone to check my work here. I already turned in the homework with my hunch, but now I just want to check my work because it is killing me not knowing 100% :) I am having strong conflicting thoughts on particular parts and thought I'd post it here for clarification. I will...
  31. T

    Find the Tension in a Flexible Chain Resting on a Cone

    Homework Statement A loop of flexible chain, of total weight W, rests on a smooth, frictionless right circular cone of base radius r and height h. The chain rests in a horizontal circle on the cone, whose axis is vertical. Find the tension in the chain. Homework Equations Virtual work, but...
  32. P

    Finding Static Equilibrium: Solving for Unknown Angles

    Can anyone help me with this question! I know to solve this problem, you have to set ΣF and ΣM =0, but what do you do with angle? (It's P.31 in the bottom)
  33. Z

    Static equilibrium and torque

    Homework Statement A 10 000-N shark is supported by a rope attached to a 4.00-m rod that can pivot at the base. Calculate the tension in the cable between the rod and the wall, assuming the cable is holding the system in the position shown in Figure P12.49. Homework EquationsThe Attempt at...
  34. Z

    Vector multiplication in static equilibrium

    Homework Statement A 1 200-N uniform boom at 65 degrees to the vertical is supported by a cable at an angle of 25 degrees to the horizontal . The boom is pivoted at the bottom, and an object of weight = 2 000 N hangs from its top. Find the tension in the support cable Homework EquationsThe...
  35. Z

    Static equilibrium involving toque

    Homework Statement Sir Lost-a-Lot dons his armor and sets out from the castle on his trusty steed (Fig. P12.19). Usually, the drawbridge is lowered to a horizontal position so that the end of the bridge rests on the stone ledge. Unfortunately, Lost-a-Lot’s squire didn’t lower the drawbridge far...
  36. O

    Easy statics problem -- Block being hoisted by a pulley and rope

    I drew a FBD about point A and came up with the two equations: ∑Fx=0 20sinθ - T-ab(cos70)=0 ΣFy =0 -20cosθ + T-ab(sin70) -20=0 My answer is not coming out so I either messed up on the FBD or the equations, some help would be appreciated. I'm on 3-10 by the way.
  37. Sarah00

    Static Equilibrium: Net Force & Torque = 0

    Homework Statement 2. Homework Equations Net Force = 0 Net Torque = 0 The Attempt at a Solution I know how to deal with these problems. My question is: What the word 'minimum' means here? A zero normal force over the second support point?
  38. A

    Tension force and a board fixed to a flat surface

    A heavy board is fixed to another flat surface along its entire upper edge and not moving. How can I find the tension force that is acting on the board? Is it the same as if the board would be fixed to a string in the middle of the upper edge and hung and then the tension would be T=mg?
  39. rpthomps

    What Is the Minimum Coefficient of Friction Needed for a Sphere Against a Wall?

    Homework Statement A uniform sphere of radius R is supported by a rope attached to a vertical wall,as shown in the figure. The point where the rope is attached to the sphere is located so a continuation of the tope would intersect a horizontal line through the sphere’s centre a distance R/2...
  40. Sarah00

    Static Equilibrium Homework: Net Force and Torque Solutions

    Homework Statement Homework Equations Net Force = 0 Net Torque = 0 3. The Attempt at a Solution At the support point , is there a horizontal force component?
  41. J-dizzal

    Static equilibrium. Friction example

    Homework Statement A woman pedals her bicycle up a 8-percent grade on a slippery road at a steady speed. The woman and bicycle have a combined mass of 76 kg with mass center at G. If the rear wheel is on the verge of slipping, determine the coefficient of friction μs between the rear tire and...
  42. J-dizzal

    Static equilibrium, machines; handheld press

    Homework Statement The handheld press is useful for such tasks as squeezing rivets or punching holes. What force P is applied to the sheet metal at E for the 64-N forces applied to the handles? Homework EquationsThe Attempt at a Solution Not sure how to get this one started, i initially took...
  43. J-dizzal

    Static equilibrium problem -- with a pulley

    Homework Statement Homework Equations sum of forces equal to zero. The Attempt at a Solution
  44. J-dizzal

    Static equilibrium, trusses/section method

    Homework Statement Calculate the forces in members BC, BE, and EF. Solve for each force from an equilibrium equation which contains that force as the only unknown. The forces are positive if in tension, negative if in compression. Homework Equations Sum of forces and moments equal zero. The...
  45. J-dizzal

    Static equilibrium of a beam, 2 force and 3 force member?

    Homework Statement Homework Equations ΣF=0 ΣM=0 The Attempt at a Solution I think i correctly identified two 2 force members at A and B. But would the system be a 3 force member? If it is i don't quite know how to solve for the missing angles. Is the problem asking for the sum of the...
  46. J-dizzal

    Static equilibrium 3D, traffic light problem

    Homework Statement The vertical and horizontal poles at the traffic-light assembly are erected first. Determine the additional force and moment reactions at the base O caused by the addition of the three 100-lb traffic signals B, C, and D. Report your answers as a force magnitude and a moment...
  47. J-dizzal

    Static equilibrium minimum cylinder mass problem

    Homework Statement Determine the minimum cylinder mass m1 required to cause loss of contact at A. Homework Equations ΣF=0, ΣM=0 The Attempt at a Solution Im not sure where to go with this one. the solution would be in terms of mass(m)
  48. J-dizzal

    Static equilibrium; pulley and inclined plane problem.

    Homework Statement What weight WB will cause the system to be in equilibrium? Neglect all friction, and state any other assumptions. Homework Equations ΣF=0 The Attempt at a Solution I can't figure out what I am doing wrong with these pully problems, I tried putting in resultant forces at...
  49. Curieuse

    Static equilibrium of a wheel

    1. Problem statement In figure, what magnitude of (constant) force F applied horizontally at the axle of the wheel is necessary to raise the wheel over an obstacle of height h=3.00cm ? The wheel's radius is r=6.00cm , and it's mass is m=0.800 kg. Homework Equations Balance of forces: Fnet=0...
  50. C

    How is the torque shared between two points?

    Figure: 1. Homework Statement We know system is in equilibrium and we are given the mass m, and the distances d, r1, and r2. We assume that the rotational inertia of the bar is negligible. What are the forces at points a and b? Homework Equations Torque = radius × Force Force = mass *...
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