What is Free body diagrams: 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. M

    Free Body Diagrams and Forces

    I don't even know how to begin this. I know that I need to somehow account for the drag force that duck 3 is causing on the first 2, but I don't know how to deal with that. I am asking for someone to help me get started, not to give me the answer.
  2. A

    I Force Generated By Leg Muscles in Free Body Diagrams

    Suppose a person is walking on the ground without slipping. For the free body diagram of just the person, only the frictional force is drawn in the horizontal direction. The force exerted by the leg muscles to generate a force against the ground is considered an internal force. What would be the...
  3. M

    I Can free body diagrams be used if friction at pivot is not negligible?

    Are we allowed to use free body diagrams in dynamic systems where there is non-negligible friction in say the rotational pivot between two linkages? If so, how to incorporate friction into the equations of motion? If not, what method allows friction to be accounted for?
  4. F

    Free body diagrams, coordinate systems origin/orientation

    Hello, When solving statics or dynamics problems, one important step is to draw the free body diagram (FBD) with all the external forces acting ON the system. The "chosen" system may be composed of a single or multiple entities. The external forces have components that must be projects on the...
  5. Like Tony Stark

    Free body diagrams for boxes, inclined planes and springs

    FIRST PICTURE I have some doubts here because of the spring... I'll tell you what forces I've drawn. For ##A##, I drew the weight and the force applied by ##B## (the normal force) on the vertical axis; and the elastic force pointing to the right on the horizontal axis. For ##B##, I drew the...
  6. E

    Mechanical advantage of a pulley system

    I don't know how the bottom two pulleys affect the top one. From what I know, the three ropes should have the same tension, the force of the body, divided between them. So if we take top one, it should have that tension on both sides, but also should support the other two pulleys below it. That...
  7. thebosonbreaker

    A question about Newton's laws & free body diagrams....

    Here I have drawn the free-body diagram for a rock (but could really be any object) which is being pulled upwards. Fa represents the applied force (let's say...by a rope) Fg represents gravity/weight of the object Ff represents friciton, i.e. the small amount of air resistance But here's my...
  8. R

    Modified Block Problem -- Block on top and on the side

    << Thread moved to the schoolwork forums from the technical forums, so no Homework Template is shown >> The problem is a modified version of two basic block problems. This is my work so far, but I end up with two equations for acceleration from m1 and m2, I don't understand how to use both...
  9. K

    I Designing a Car with Multiple Boxes: Free Body Diagrams

    hi, i am studying about design the box carried on car. i am really stuck in how to draw free body diagram for when 3 or more boxes stack together on car running and braking. there are many example with 2 boxes but i don't know why i can't find any case with 3 or more boxes thanks in advance
  10. M

    Forces and Free-Body Diagrams in Real-World Scenarios

    Homework Statement I am just going over my class notes and I just wanted to clear up a few concepts regarding forces and free-body diagrams -- I'm either missing some forces or adding one too many: Identify the forces acting on objects in each of the following situations and draw a free-body...
  11. G

    Calculating Forces on an L-Bracket for Supporting Large Pipework

    I am installing an L-shaped bracket into a brickwork chimney to support some large pipework. I am trying to work out the forces in each fixing to ensure that I won't be pulling the bracket off the wall once the pipes are filled with water. I've tried drawing the free body diagram and to resolve...
  12. Janet1234

    Drawing free body diagrams (torque; rotational motion)

    Homework Statement A 500-N person stands 2.5 m from a wall against which a horizontal beam is attached. The beam is 6 m long and weighs 200N (see diagram below). A cable attached to the free end of the beam makes an angle of 45 degrees to the horizontal and is attached to the wall. Homework...
  13. J

    Free Body Diagram lab report -- General Question

    < Mentor Note -- thread moved to HH from the technical forums to use a scpecific schoolwork problem to illustrate the general concept of torque in a FBD > I'm writing up a lab report for Physics class and I have to draw FBDs for torque being applied to a ruler resting on a pivot point. I've...
  14. C

    Can you me understand free body diagrams

    Free body diagrams are where you simplify each object to a point and draw all of the forces acting upon it. I am having difficulty understanding it entirely and it would really help to just have a bunch of examples of free body diagrams. If you have a link to a bunch that would be great. I...
  15. C

    Electric Charge and Force free body diagrams

    Homework Statement A positive charge Q1 = 7.4 μC is located at a point X1 = -2 m, a negative charge Q2 = -9.7 μC is located at a point X2 = 3 m and a positive charge Q3 = 2.1 μC is located at a point X3 = 9 m. Draw free body diagrams for the electric force acting on Q1, Q2 and Q3. Find the...
  16. N

    Friction Problem Homework: Find Angle & Weight of Box

    Homework Statement An initially stationary box of sand is to be pulled across a floor by means of a cable in which the tension should not exceed 1100 N. The coefficient of static friction between the box and the floor is 0.35. (a) What should be the angle between the cable and the horizontal in...
  17. alexandria

    Net acceleration, free body diagrams, velocity, force normal

    Homework Statement Homework Equations relevant equations are provided with each question below The Attempt at a Solution please check my solutions to ensure they are correct. thanks. a) [/B] b) Calculate net force: Fnet = FA + Ff + Fg Fnet = (1.20 x 104 N [up]) + (1.40 x 103 N [down])...
  18. C

    Symbolic relationship between the input and output load

    Homework Statement A testing device has the applied load located at the end of a loading bar. The loading bar is connected by a pin to the post. Find the symbolic relationship between the applied load(the "input" load) and the effective load applied the specimen(the "output" load). Homework...
  19. Mr Davis 97

    Representing Free body diagrams

    I have a simple question. I know that the objects that we work with in introductory physics are point particles. Thus, say we have a picture frame that is put on a wall. There is a wire holding it up, where the wire is attached to the top right and the top left corners of the frame. The passes...
  20. W

    Setting up systems of forces and free body diagrams

    Homework Statement Suppose I've got a static mass on a downward plane. (For instance a car on a drive way). How would you set up this free body diagram? Homework Equations F = f1+f2...etc The Attempt at a Solution My preference is A, but I've seen it displayed in examples in my book as B...
  21. K

    Classical Practicing Free Body Diagrams & improve problem solving skills

    Hi, I once considered myself enough to be decent enough to solve some problems but lately I'm thinking to revisit and start solving problems again. I would like to know whether there is a book good which has problems (starting from basic to tough ones) for practicing free body diagrams. The book...
  22. K

    Free body diagrams and Newton's Law

    Homework Statement 2 masses, m1 and m2 are connected by a cord and placed on a frictionless table as shown in the diagram below. m1 slides on the frictionless table while m2 is hanging from a light frictionless pulley. What would be the mass of the hanging mass m2 if we know that the tension in...
  23. D

    Is this Free-Body Diagram Correct?

    Homework Statement I have to draw a free body diagram representing the motion of an object @ a given point in time. This diagram is for section 1. It's of a 1.25 kg cart with a 0.6 kg can attached to it with a pulley-system. When the can drops, the cart begins to move. In section one, when the...
  24. M

    Resources for Practicing Drawing Free Body Diagrams

    I am absolutely clueless when it comes to drawing free body diagrams. I think I understand the concepts but as soon as I see an unfamiliar system I have no idea what goes where. Are there any resourcess that provide a large number of practice problems (with solutions) for drawing free body...
  25. M

    Help Drawing Free Body Diagrams?

    Homework Statement At a construction site, a small crane is raising two boxes of nails on a plank to the roof. One box has already been opened and is half full, while the other box is new. The boxes, including the nails, weigh 10kg and 20kg, respectively, and are both the same size. If the...
  26. H

    Weight in an elevator? Free body diagrams

    A 60kg student is standing on a scale in an elevator that measures weight in Newtons. Calculate the reading on the scale if the elevator is accelerating down at 4 m/s^2...when the elevator is accelerating up at 4 m/s^2... and in free fall. Not sure if my work/answer is correct accelerating...
  27. P

    Discover How to Select Internal Forces for Free Body Diagrams

    Homework Statement http://postimg.org/image/4lvunjeoz/ Solution: http://postimg.org/image/v1d7gilef/ When you have to calculate the internal forces at a point, how do you decide which forces are included in the free body diagram? For D, why isn't the rectangular bit of the distributed load...
  28. P

    Solving Free Body Diagrams Homework

    Homework Statement http://postimg.org/image/i7phx5pp1/ Im trying to draw an FBD for this, but I don't know how the treat the distributed load or what forces the thing at E contributes. Is it some kind of support? For the distributed load, I don't know what part of it the 800N/m and...
  29. F

    Solving Free Body Diagrams with 1.9kg Object & F1=5, F2=2

    1. The question I'm struggling on has been answered on here before but with different values. Here is the link to the question https://www.physicsforums.com/showthread.php?t=344213 but on mine I have a 1.9kg object and F1=5 and F2=2. I figured out that the Y components are 0 for both of...
  30. A

    What is the convention for writing vector magnitudes in free body diagrams?

    Do you normally write the magnitude of the vectors in free body diagrams? I have homework on this. Is there any convention when writing the magnitude?
  31. 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...
  32. L

    Free Body Diagrams: Easily Analysing Photos & Sketches

    Hi, When looking at a photo or sketch, I find it hard to take out the important bits and turn it into a freebody diagram. I am doing this question (pic attached). Im quite unsure how to even begin. I've though of a few ways to start analysing it. The first way analyses AD as a whole. And...
  33. B

    Help drawing free body diagrams

    Homework Statement The picture attached is the problem. Also given is the constant acceleration of 2m/s^2, a frictional force of 75N, and the mass of block A is 25kg. Homework Equations The Attempt at a Solution I just need help with drawing the free diagram part involving the normal force...
  34. T

    What is the significance of F being a roller joint in this system?

    Homework Statement Assume the system is massless. The Attempt at a Solution Here is my quick attempt at drawing a free body diagram for this system: What I am not sure about is the direction of the force at F. Should the force be A or B?
  35. E

    Question related to SHM and free body diagrams

    Homework Statement Draw three free-body diagrams showing the forces acting on a toy suspended by a vertical spring. The diagrams should show the situations when the toy is at its equilibrium position, and above and below the equilibrium position. Homework Equations The Attempt at a...
  36. S

    Software to draw free body diagrams and vector diagrams

    Hello Could anyone recommend me a software to draw draw free body diagrams, vector diagrams, spherical/cylindrical coordinates systems etc. I am doing a project on electromagnetics and I am supposed to put everything in a digital format. Thanks
  37. J

    Finding Applied Force with Free Body Diagrams (Grade 12 Physics)

    Homework Statement You have a 10kg object that is thrown down a building. The distance from the ground to the building is 50m. The initial velocity of the object is 5 m/s. What is the applied force and what force does the object hit the ground with? Homework Equations Fapp= Fnet+Fg...
  38. H

    Software for drawing simple objects and vectors (free body diagrams)?

    Hi. I'm looking for a drawing tool which may help me draw simple figures with vectors and angles. I've tried many but they're so complicated... e.g. Photoshop, Power Point, Edraw, and some others. The ideal one would be one which is designed for this... I mean a program that has a tool, for...
  39. A

    Uniform Circular Motion Free Body Diagrams

    Homework Statement A circular-motion addict of mass 82.0 kg rides a Ferris wheel around in a vertical circle of radius 14.0 m at a constant speed of 7.10 m/s. (a) What is the period of the motion? What is the magnitude of the normal force on the addict from the seat when both go through (b)...
  40. MysticDude

    Drawing Free Body Diagrams for Acceleration Problems

    Homework Statement Draw free body diagrams: A rectangular block being accelerated on a horizontal, frictionless surface. A skydiver who had just jumped from a plane and hasn't reached terminal velocity. A cube being accelerated up a 30° incline with μk > 0. A pendulum bob that has just been...
  41. T

    Free body diagrams for springs and dampers in torsion

    Homework Statement I have been having a little discussion with a friend. We both know that for a spring/damper system in parallel like shown below, the associated free body diagram is correct. http://img337.imageshack.us/img337/2023/para0.jpg But when it comes to the same system in...
  42. M

    Can someone me out with free body diagrams

    **a horizontal force with magnitude A is acting on a pulley as shown. the two masses p and P are moving together, same acceleration. p is trying to fall to the left but the tension from the rope and the static friction is keeping it in place. Everything else you need to know is in my two...
  43. Y

    How to determine direction of forces in free body diagrams?

    For instance, in the below diagram: [PLAIN]http://img101.imageshack.us/img101/3205/59914396.png How do you know if the reaction force on the beam is in Direction A or B? How do you determine the correction direction?
  44. A

    Mechanics & Free Body Diagrams

    Homework Statement Please see the attachment, Q2 Homework Equations \sumFx = 0 \sumMA = 0 The Attempt at a Solution for part A, i get 14123N as the tension, moment at C about B, 9.8x1000x5 = 49050 49050/7 = 7007N tan-1 (4/7) = 29.74o TSin(29.74) - 7007 = 0 TSin(29.74) = 7007...
  45. D

    Free Body Diagrams on friction less surface

    1. A frictionless surface is inclined at an angle of 34.4° to the horizontal. A 270-g block on the ramp is attached to a 75.0-g block using a pulley, as shown in the figure below. (a) Draw two free-body diagrams, one for the 270-g block and the other for the 75.0-g block. (b) Find the tension...
  46. E

    Simple Problem. Finding Forces using free body diagrams.

    Hey all, here is a simple problem provided as a review for our final by my professor. I think I have everything right, but if history offers any insight into the future, I'm dead wrong. Any help is greatly appreciated.Homework Statement A 30kg box sits on a 10kg wagon. the wagon is pulled by...
  47. J

    Drawing Free Body Diagrams with torque

    Homework Statement This is a review problem i was given for my final exam tommorow, I am stuck on 1 problem, even with the answer key I am not understanding it.(also sorry but the picture won't copy from MSword, but its a cylinder rolling up a hill) (B) When the lander hits the surface...
  48. M

    How do I draw a free-body diagram for an object sliding down an inclined plane?

    Hello there , I don't know how to draw free body diagrams , so can u illustrate to me how to draw an FBD for an object sliding down a ramp like this one. http://ffden-2.phys.uaf.edu/211_fall2004.web.dir/Jeff_Levison/freebody_diagram.jpg illustrate this in details , please Thanks
  49. H

    Free Body Diagrams: Static Equilibrium

    Homework Statement Blocks A & B each have mass 5kg, and all contact surfaces are frictionless. Determine the force F needed to keep the blocks in static equilibrium, and the forces on all contact surfaces. Homework Equations I know I need to find where Fx= 0 and where Fy= 0. The Attempt...
  50. G

    Free body diagrams and adding forces

    Homework Statement In each of the two free-body diagrams, the forces are acting on a 2.6 kg object. For each diagram, find the values of ax and ay, the x- and y-components of the acceleration, with F1 = 5 N and F2 = 3 N. Picture is attached. (a) Diagram A ax =____ m/s2 ay =____ m/s2 (b)...
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