What is Force diagram: Definition and 70 Discussions

A free body diagram consists of a diagrammatic representation of a single body or a subsystem of bodies isolated from its surroundings showing all the forces acting on it.
In physics and engineering, a free body diagram (force diagram, or FBD) is a graphical illustration used to visualize the applied forces, moments, and resulting reactions on a body in a given condition. They depict a body or connected bodies with all the applied forces and moments, and reactions, which act on the body(ies). The body may consist of multiple internal members (such as a truss), or be a compact body (such as a beam). A series of free bodies and other diagrams may be necessary to solve complex problems.

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  1. A

    Simple Static 3-Particle Model

    Diagram Integrate pressure for each particle: Add normal force and weight Sum all the forces in the x and y direction to get:
  2. D

    B Torsion Involving an Off Axis Thrust

    I have tried to draw a force diagram to illustrate the problem. Suppose I have a 2m, 100kg uniform rod with wheels at the bottom. Center of mass is middle of rod. I want to accelerate this rod horizontally while it remains perfectly vertical (constant angle). But the force is coming from a rod...
  3. paulimerci

    Find the magnitude of the electric force from 3 charges at vertices of a cube

    There are three charges with +1 μC and −1 μC, are placed at the opposite corners of a cube with edges of length 1 cm, and the distance from P to B is 1cm 2. I labeled them as A, P, and B, which is shown in the diagram below. Since we need to find the magnitude of the charge at point P and the...
  4. ElectricVocaloid

    Dynamics problem (force and torque analysis) of a human finger

    I was having trouble with a physics problem (string tension dynamics) In this case I have a model that simulates the phalanges of a human finger. Each phalanx is a block of mass m1, m2 or m3 respectively. And to simplify it, consider the 3 equal masses. These phalanges are linked by joints that...
  5. P

    B Confused about force body diagram for 2 body collision

    I'm trying to understand Newton's third law in the context of collisions. Assume that one body has mass M kg and is traveling in the positive x direction with acceleration A m/s^2. Assume that the second body has mass m kg and is traveling in the negative x direction with acceleration a m/s^2...
  6. S

    How Does the Direction of Normal Contact Force Affect Shelf Stability?

    Judging from FBD of the shelf, the answer will be either (B) or (D) because there should be horizontal force to the left to balance the horizontal force to the right by F, and by considering the torque, I think the answer will be (B) But I am confused about the direction of the normal contact...
  7. S

    Force diagram of two rods hinged together

    Picture from the question Options: Option (B) is wrong because the both reaction forces have to be slanted since they are resultant of normal force and frictional force. I think option (C) is wrong because taking the point where the two rods meet as point P and comparing the torque produced...
  8. P

    Is this force diagram correct?

    Trolley should have zero acceleration.
  9. E

    Force diagram for integrated exercise

    Hello, Can someone help me out with this one. I solved the exercise but didn't get the right answer so I went searching on internet for solutions. It seems something was wrong with my force-diagram. In my force diagram I had another force included excerted by the wire on the post, since the...
  10. opus

    Force Diagrams for Sliding Block on Inclined Plane

    Homework Statement This is more of a general question, not specific to any problem. I am not too good at drawing force diagrams so I was hoping I could post an image and get some guidance on how to find the forces acting on the object. In this case, we have a block sliding down a plane of angle...
  11. Alice_in_Wonderland

    Two linebackers simultaneously hit a quarterback: Force Diagram

    Homework Statement Two linebackers simultaneously hit a quarterback, who has a mass of 90 kg. One linebacker exerts a force on the quarterback of 500 N, 25° N of E. The other linebacker exerts a force on the quarterback of 450 N, 60° S of E. Determine the net force acting on the quarterback...
  12. I

    Force Calculation -- Hydraulic cylinder and a rotating arm

    Hi There, Long time reader, first time poster.. I hope someone out there can help me. I'm designing an add-on to an existing piece of equipment and I'm unsure of how to calculate the resultant force output from a hydraulic cylinder. On a straight push, the chosen hydraulic cylinder has an...
  13. B

    Direction of The Force of a Wall Exerted on a Rod

    Homework Statement A rod is attached to a wall in such a way it can swivel. In this case: In which direction does the force (of the wall on the rod) point to? Here are two examples (see under attached files), but the the direction of the force is different. Why? Is maybe one of the pictures...
  14. B

    Why are the angles in rope equilibrium the same?

    Homework Statement Between two parallel walls we tighten a rope. One end of a rope is tied a little higher on the wall than the end on the opposite wall. On the rope we put a pulley with mass m which slides to equilibrium position. Homework EquationsThe Attempt at a Solution I assumed that in...
  15. H

    Find the force between 2 blocks

    1. The problem statement, all variables and given/known data Homework EquationsThe Attempt at a Solution B at rest. A moves 7m/s and bump into B. Object A is frictionless. Object B not, coeff of friction = 0.2. g = 9.8 m/s2 After collision both objects moves together with speed 2 m/s to the...
  16. E

    What are the forces on the center of mass?

    Homework Statement [/B] A light rope passes over a light frictionless pulley attached to the ceiling. An object with a large mass is tied to one end and an object with a smaller mass is tied to the other end. Starting from rest the heavier object moves downward and the lighter object moves...
  17. E

    How do write the force diagram for the following situation?

    Homework Statement We have a crate sitting on a scale that is on the surface of the Earth. We want to come up with the value of the acceleration due to gravity, ## g ##, when we take into consideration the rotation of the Earth. Homework Equations In the book, here's how they go about this...
  18. S

    Can rotating shafts experience changes in deflection due to inertial effects?

    I am curious how the deflection of a shaft changes due to rotation. In the force diagram image the green arrows show the rotational fixture locations and the purple arrow show the location of the applied force. The second image shows the deflection during a static test. If the force is applied...
  19. E

    B Gyroscopic precession force diagram

    Hi, I've been learning about gyroscopic precession recently and I feel like I get it. I understand that when the flywheel of a gyroscope is spinning its angular moment plus the angular moment created by the torque from the force of gravity makes it turn. But I were thinking about the forces in a...
  20. H

    Force diagram of a spinning mass tied to a string

    Homework Statement In an effort to rev up his class, Mr. H does a demonstration with a bucket of water tied to a 1.3-meter long string. The bucket and water have a mass of 1.8 kg. Mr. H whirls the bucket in a vertical circle such that it has a speed of 3.9 m/s at the top of the loop and 6.4 m/s...
  21. D

    Finding height dropped from Force vs. Time graph

    Homework Statement A pumpkin was dropped from a balcony of a skyscraper. The pumpkin happened to land on a sidewalk force sensor and the below data was collected. The pumpkin weighs 2.7kg. a) From what height was the pumpkin dropped? b) From what floor of the skyscraper was the...
  22. StarWarsNerd

    B Calculating Linear and Angular Quantities from Applied Force

    In the image above, a centroid with radius 1 is depicted. F1 is pointing directly at point A (which is the center of the circle), and F2 is pointing directly at point B. The radius for finding the torque would be the perpendicular between the center of the object and the force vector, so r1...
  23. C

    Shear Force Diagram: 45N at 0.6m from B vs. 0.5m from D - Homework Question

    Homework Statement In this question , the 45N is acting at 0.6m from B ... why the author put the 45N forces at D in the shear force diagram ? Is it wrong ? Homework EquationsThe Attempt at a Solution IMO , the 45N should be put at 0.5m from D . Correct me if i am wrong
  24. S

    Physical interpretation of free body force diagram

    Homework Statement Free body force diagram question, where I have selected the best answer but the diagram doesn't ring completely true (see diagram uploaded). I think mathematically the diagram is sufficient but it doesn't properly represent the situation. Do you agree? Homework EquationsThe...
  25. C

    Shear force diagram and bending moment diagram

    Homework Statement theoretically, bending moment should ends at bending moment = 0 , am i right ? Homework EquationsThe Attempt at a Solution Here's my sketch of SFD and BMD ,my bending moment doesn't return to 0 , which part of my working is wrong ... to find bending moment (M) , i get M...
  26. C

    Correct Shear Force and Bending Moment Diagrams for Beam Analysis

    Homework Statement There are 2 graphs in the notes , the first represent the shear force diagram , while the secon d one represent the bending moment diagram... In the notes , we can see that the gradient of the force per meter to the right of B is decreasing ... Homework EquationsThe Attempt...
  27. H

    Moments and shear force diagram

    Hi Can someone please help me with this problem: A beam is 16m long and rests on two supports, 10m part. the right support is 4m from the right-hand end. The beam carries a uniformly distributed load of 408 kg/m between the two supports and concentrated loads of 2kN at the left end, 0,153 tons...
  28. J

    I Does mass density affect load distribution on barbell?

    Had an argument with a few guys at the gym today. I told them that loading a barbell with 100 on each side instead of 2 45s and a 10 causes more pressure on your spine. This example is in reference to someone performing a low bar squat in which the bar has contact points across the entire back...
  29. D

    Producing a shearing force diagram and bending moment curve

    Homework Statement A box shaped vessel, of ##4## compartments and ##80m## lenght, light displacement of ##800## tonnes loads ##200## tonnes in the first compartment and ##200## tonnes in the last compartment. Produce the shearing force diagram and bending moment curve. Homework Equations 3...
  30. N

    Force & Motion Homework: Force Diagrams, Velocities & Accelerations

    Homework Statement A small box (mass m1) is placed upon a large box (mass m2); the large box i placed on a horizontal table. The boxes begin a rest on the table. The lower box is hit by a horizontal blow at the time t=0 resulting in a initial velocity v0. The frictioncoefficient between all...
  31. Mr Davis 97

    Force diagram of a suction cup

    I am a little confused about how to construct a force diagram for a suction cup, like a plunger, as it is stuck to a wall. First, I know that the cup is not accelerating, so the gravitational force pulling down on the cup has to be met with an equal but opposite force vector pointing up...
  32. C

    Magnetic force to hold machine and required Torque to drive

    Homework Statement The robot crawler has a magnet attached to it. The idea is to get the crawler up the wall. What is the magnetic force required to hold a object (in this case) a robot crawler with an attached Magnet? Is more magnetic force required to hold the crawler while it goes up the...
  33. hdp12

    Internal Force Diagram for Rigid Body and Distributed Load

    I'm working on a homework problem for Statics and I'm stuck. Could someone please help?Problem: Draw the internal force (N,V,M) diagrams and include all significant figures Here is all of my work: Resulting F from W1: W(x) = W1 ∴ F2=∫02b W1dx eq (1) ⇒ F2 = W1⋅2b x1 = (F1)-1 ∫02b W1dx =...
  34. 1

    Why is there a vertical force on the pin in this static equilibrium setup?

    Q: Why does the pin have a vertical force in this diagram (Static equilibrium)? The diagram depicts as follows: A mass (M) sits a a distance (d) away from the end of a board of length L. The board has a mass of m and is held to a wall by a pin and string. The string has a tension (T) and is at...
  35. P

    Does Normal Force change with new Force diagram?

    All degrees are measured from the positive x-axis. FG = Force of gravity FN = Normal force FT = Force of tension Problem: A skier is being pulled up a 15° incline by a rope. I'm solving for FT. The only forces acting on the skier are FG, FN, and FT. Attempt at a solution: Initially, my...
  36. G

    Find Forces on Hand and Arm Holding a Ball

    Homework Statement When an object is static (not moving), forces and moments must balance to zero. A moment here is defined as the force applied to an object multiplied by the distance from the point of rotation (torque). A simple way of thinking about moment balances is to consider a seesaw...
  37. K

    Calculating Centripetal Force: Diagramming and Solving for X and Y Forces

    How would you go about proving that centripetal F=(mv^2)/r by diagramming and solving for the magnitude of the forces in the x and y direction? For example, suppose I wanted to calculate the work done in the radial direction by centripetal force.
  38. K

    What is the Correct Electric Charge Force Diagram for a Single Charge?

    I drew a force diagram of one charge with gravity downward, electric force to the right, and tension at 20 degrees left of +y. I summed the forces in the x and y directions: Fy = Tsin20° - mg = 0 T = 0.1434 N Fx = kq^2 / r^2 - Tcos20° = 0 q = 6.29 x 10^-12 C The correct answer is...
  39. A

    Can a shear force diagram be a function of applied load P?

    …or must it be of displacement, x? In a shear force, V (or bending moment, M) diagram, isn't it usually the shear force (or bending moment) plotted as a function of displacement, x? When someone asks to "draw the shear force and bending moment diagrams as a function of the applied load...
  40. B

    Force Diagram, Position vs Time Plot: Construct, Calculate, Sketch

    The vertical motion of an elevator is recorded and a Position vs Time plot is generated. The plot is shown in the image attached. 1. Construct a scale drawing of the associated Velocity vs Time plot complete with axis labels. 2. Calculate the average acceleration for the time interval t...
  41. B

    Rolling without slipping force diagram

    This is the second part of a 2 part problem. The first part is: A solid disc is rolling down a 30 degree incline from rest. a. draw the force diagram for the disk. b. write the equations for both translation and rotational motion c. Find the linear acceleration of the center of mass. d...
  42. F

    Tension and Force diagram help

    Two buckets of sand hand from opposite ends of a rope that passes over an ideal pulley. One bucket is full and weighs 118 N; the other is only partly filled and weighs 58 N. After the buckets are released and allowed to move what is the tension in the rope I drew a force diagram but all I...
  43. Femme_physics

    Forces gears cause to the shaft (spur gears) - force diagram

    Homework Statement Describe the forces acting on the shaft AB Homework Equations The Attempt at a Solution I've ignored the bearings for now... but I know each of them has 2 forces, 1 in the radial direction and the other in the tangential direction ... Anyway, this is my diagram (sans...
  44. D

    Drawing a shear force diagram with loads working at an angle

    I was wondering how you incorporate an angled load into a shear force diagram? So far I've only been working with vertical loads and I've looked through my entire book without finding an example with loads at an angle, so I'm not sure what to do here. I know I have to end up at 0 so I see I...
  45. PhizKid

    Force diagram for ring/bead problem

    Homework Statement A ring of mass M hangs from a thread, and two beads of mass m slide on it without friction. The beads are released simultaneously from the top of the ring and slide down opposite sides. Show that the ring will start to rise if m > 3M/2, and find the angle at which this...
  46. D

    Uniform cylinder force diagram

    Homework Statement A uniform cylinder of mass m and radius R rests in equilibrium against a rough plane that is inclined at an angle α to the horizontal. The cylinder is supported by a cord under a constant tension, wrapped round it, so that the cord leaves the surface of the cylinder...
  47. S

    Finding point loads in shear force diagram

    Homework Statement I have a shear force diagram and I am asked to find the magnitudes of the point loads and where are they situated My question is, what am I looking for to find the point loads in a shear force diagram? Homework Equations The Attempt at a Solution
  48. J

    What Could Be Wrong with My Shear Force Diagram?

    I have drawn the following shear force diagram however it says it is wrong. Could somebody please explain to me what is wrong with it. The points in the diagram are 0 then -4 then 1.25 then 1.25, then back to 0.
  49. W

    What does a shear force diagram for a cantilever look like?

    I have the problem below, my question is what should the shear force diagram look like, I know its just a simple cantilever so does that mean the shear force diagram will be very rectangular looking?
  50. S

    Rock climber force diagram and acceleration

    A 70kg climber is dangling over the edge of an ice cliff. He is roped to a 940kg rock located 51 m from the edge. The ice is frictionless, and the climber starts to accelerate downward. a) How would you find the acceleration of the climber? Would you use the force diagrams for the rock and...
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