# What is Free body: Definition and 288 Discussions

The term free body is usually associated with the motion of a free body diagram, a pictorial device used by physicists and engineers. In that context, a body is said to be "free" when it is singled out from other bodies for the purposes of dynamic or static analysis. The object does not have to be "free" in the sense of being unforced, and it may or may not be in a state of equilibrium; rather, it is not fixed in place and is thus "free" to move in response to forces and torques it may experience.

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1. ### Two masses on a slope with a connected tension force

I derived an equation but I have no idea how I can find the mass of the unknown without the normal force in either the x or y direction
2. ### 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. ### Free body diagram for two-force members

Hoping someone can chip in and help me understand a problem when it comes to two-force members. I have a structure as shown below. Essentially its a single body attached at 3 points with pin joints. My question is, is it appropriate to treat each of the left and right side as individual...
4. ### 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?
5. ### Engineering Is My Free Body Diagram for a Frame Accurate?

can you check if I sketched it correctly? And please if you know any good resources refrence it.
6. ### B Question about a simple free body diagram

In this diagram, if the system begins by being held static, and then at time ##T## release of all components occurs, at all times ##>T##, until vertical movement stops upon vertical block ##m## making contact with the Normal Force at the base of block ##M##, will the lateral acceleration of...
7. ### Free body diagram for an inverted pendulum in the rolling sphere

So, to obtain the motion equations I initially plotted the free-body diagram (see picture). Then I’ve tried to get equations, but I’m not sure, do I have done it rightl. I will be gratefull if someone could help me.
8. ### I How can you make a free body diagram for someone running then sliding?

Let's say you are riding a bike very fast, and then you sharply turn into a slide (where the bike is sliding perfectly sideways). I'm trying to calculate the angle that the bike would be leaning at, but I'm having trouble creating the free body diagram. Right now I have the normal force and...
9. ### Free Body Diagram for a Piece of Gum on the Underside of a Desk

So I’m a high school physics teacher and I came up with the question above. However I haven’t given it to my students because I’m not sure what the answer would be. There is a force holding the gum up, and that force must balance the force of gravity. I’d probably call that an applied force, so...
10. ### Finding Radial Force from Free Body Diagram

I have a question regarding a homework exercise. My professor asked me to find the radial force in the free body diagram in the image included. There is a weight Fz from above and it is assumed that it is countered by the vertical component of both the Ff (friction force) and the Fn (normal...
11. ### Engineering Need help verifying symbolic calculations for an FBD statics problem

So basically, I got close to a zero for my solution to this problem. I'm guessing based on the posted solutions that I wasn't able to get partial credit due to the fact that my coordinate axis was aligned with the slender bar and not in its usual perpendicular position. This resulted in...
12. ### 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...
13. ### Free body Diagram of a Plank resting on two Cylinders

I have put a picture of the problem above. The picture below shows my free body diagram. Fg is the component of the gravitational force in the direction fo the tangent at the point of contact and Ff is the frictional force between the plank and cylinder. I put Ff in the opposite direction as Fg...
14. ### Free body diagram -- Ball rotating on one arm of a Y shaped pole

To start off with, I can't seem to interpret the FBD here. Here are my drawing: and what I interpret as. From here, I feel like I can (it's wrong obviously but I'm not sure why) state that sin theta = o/h = o/mg = N/mg , so N= mg sin theta? Thanks
15. ### Need Help with Free Body Diagram of Oil & Gas Packer Tool

Has anyone created a thread on Free Body Diagram on assembly having many components ? For example a Casing having premium threads in both end and a set packer within it. What would be the FBD equations to determine various forces and reaction forces
16. ### 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...
17. ### Understanding Free Body Diagrams: Explaining the Forces on a Compressed Board

Hello everyone. I find the following problem confusing. A board sandwiched between two boards in the figure below weighs 95.5N. If friction exists between the middle and the compressing boards, draw the free body diagram of the middle board. Below I attached the diagram found in the solution...
18. ### Analyzing Forces & Electrons: Free Body Diagram

Hi i am posting this to double check my work. Please help and feel free to ask any questions. I posted a picture of my work and what i currently have. 1. Homework Statement Two small insulating objects are hung from strings attached to the ceiling. The masses of each object is 0.0076 kg. The...
19. ### Calculating tensions and acceleration

Homework Statement A mass M1 is sliding across a table with coefficient of kinetic friction μk. A string is tied to this mass and runs over a pulley, drops vertically and is tied to another mass M2 which is falling. The pulley is connected to the table by a support. The pulley is a solid...
20. ### What are the equations for circular motion on a Ferris wheel with R2D2?

Homework Statement 3. Consider R2D2 (a droid) with mass 30kg riding on a Ferris wheel with diameter 25m, with a velocity of 2.8m/s. a) Compute the free body diagram for R2D2 at the exact top, exact bottom and at both horizontal positions. Remember to include gravity. (Note: The forces act in...
21. ### Free body diagram on a block pushed against a ceiling

Homework Statement A 2kg block is being pushed along a ceiling with friction by an angled force of 70 degrees. I'm asked only for the free body diagram. Homework EquationsThe Attempt at a Solution I figured both the gravitational and normal force would point downwards, but the force applied at...
22. ### Calculating Free Body Diagram Forces

On EngineersEdge.com they have a free body diagram of a scissor lift https://www.engineersedge.com/mechanics_machines/scissor-lift.htm Can anyone explain how the Fy, Fx components are determined? What is specifically confusing to me is how Fy is opposite in direction given the system. To me...
23. ### Determine the forces acting on the two rods - Free body diagram

Homework Statement Determine the forces acting on the two rods in the figure. Explain which stresses that act on the rods and the bolts holding the rods to the brackets in point A and C. Homework Equations ∑Fx = 0 ∑Fy = 0 ∑Fz = 0...
24. ### Free body diagram of a preloaded system with a gasket

Hello,Ive got a question and wondering if there is someone that could help me? I would really appreciate it! I am studying for an exam that I am going to have in a couple of weeks and it has been going great besides that I have been stuck on a question about tension in a preloaded system with a...
25. ### Statics problem free body diagram

Homework Statement Homework EquationsThe Attempt at a Solution why are my reactions at A considered wrong? I know that AC and DC are two force-members
26. ### Statics free body diagram (frames and machines)

Homework Statement Homework Equations Trying to find the reaction forces at E. But, I am kinda confused about drawing the free body diagram for each member. I know that member AD and CB are two force members. What is wrong with my free body diagram then? The Attempt at a Solution i...
27. ### 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...
28. ### Translational + Angular Acceleration of Free Body (not fixed)

Imagine a long brick in outer space. You apply a force tangential to the center of mass. The brick accelerates in a transitional and angular fashion. There are no constraints or fixed axis. How would I calculate the translational and angular acceleration? I would like to run some simulations...
29. ### 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
30. ### How can I draw a free body diagram of a rotating wheel?

I am currently performing failure analysis on an A356 Aluminum alloy wheel subjected to rotational loading, with a maximum load of 650 kgf and a torque of 4600 Nm. Cracks formed in the wheel after 1.3*10^6 rotations. My job is to perform a stress analysis to determine the regions of maximum...
31. ### Calculating Reaction Forces on Cylinders Resting on an L Profile

Homework Statement Two cylinders, each with a mass of 10kg, are lying on an L profile. Neglect the thickness and weight of the L profile. Calculate the reaction force in b and e. Homework Equations G = mg The Attempt at a Solution So I tried to make a free body diagram of the cylinders. I...
32. ### Free body diagram of a sailboat

This is a practical issue I've trying to resolve by understanding the physics. While I talk sailing jargon, ultimately this is a question of simple torsional forces on a body. So: In a high wind, when heeled over, my boat does what's called "rounding up"; it turns sharply into the wind -...
33. ### 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...
34. ### Free Body Diagram of 3-Bar Linkage. Splitting the force?

Homework Statement Hi, please see the attached file. I am trying to find the force as illustrated in the diagram. Homework Equations [/B] The Attempt at a Solution I've found the force for the 4deg beam and therefore the horizontal beam however I am unsure how to take into account the...
35. ### 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...
36. ### 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...
37. ### What would the Free Body Diagram of a Trebuchet look like?

What would the Free Body Diagram of a Trebuchet look like (FOR THE SYSTEM)? Would it be comparable to a see saw/ teeter totter? I am aware of some of the forces at play, but I feel there is some I am missing.
38. ### 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...
39. ### Free body diagram of two different objects

I was wondering if anyone can provide feedback on my free body diagram of two objects acting on each other. The question is asking for two separate free body diagrams. A force is applied to object 1, and object 1 pushes against object 2. Object 1 is on wheels and object 2 is in contact with the...
40. ### Free Body Diagram Help: Solving a System of Equations for Forces (PreCalc)

Homework Statement Homework EquationsThe Attempt at a Solution I got the components of each force. I called the Force from BA "B" and the force from CA "C" and then the force going downward on D "W" FBy=sin30*B FBx=-cos30*B FCy=3/5*C FCx=4/5*C W=-500 ~~~~~~ ΣFx= -B*cos30 + 4/5C = 0 ΣFy=...
41. ### 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...
42. ### Draw a free body diagram for the electric force

Homework Statement A positive charge Q1=7.4uC is located at a point X1=-2 m, a negative charge Q2=-9.7uC is located at a point X2=3m and a positive Q3=2.1uC is located at a point X3=9 A. Draw a free body diagram for the electric force acting on Q1, Q2, and Q3. B. Find the magnitude of the force...
43. ### Calculating Distance: Free Body Diagram for Box Sliding with Friction

Homework Statement A 250 kg box slides down the ramp and then across a level floor. The coefficient of kinetic friction along the floor is 0.20. A person see the box moving at 1.0 m/s(left) and pushes on it with a horizontal force of 140 N (right). How far does the box travel before coming to...
44. ### Free Body Diagram and directions

Hi everyone, I am an electromechanical engineering student. The last few days I am trapping into some confusion about some things. I am just going to state my question underneath. Question: First question: As they learned me at the university. When you draw a free body diagram it doesn't mind...
45. ### How do I use a free body diagram in this case?

In the above cases I want to find the acceleration a for m1. I can do it by considering m1 and m2 to be a system, which would give me a = F/(m1+m2). How can I use a free-body diagram instead to calculate the acceleration? Using a free-body diagram, m2 only affects the vertical motion by exerting...
46. ### 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])...
47. ### Determining the Free Body Diagram for a Dolly & Trailer

Homework Statement The context of this problem involves a dolly pulling a trailer, and I am trying to establish the basic free body diagram for the trailer. Is what is done so far acceptable and is this a step in the right direction? Homework EquationsThe Attempt at a Solution I am confident...
48. ### Two-Block Dynamics Problem: Determining Acceleration and Tension

Homework Statement Assuming no friction is on the plane or the pulleys and the pulley and rope have negligible mass... Determine the acceleration of each block and the tension in each cord. Block A weighs 100kg, Block B weighs 300kg. Homework Equations ΣF = ma ma = 100kg mb = 300kg The...
49. ### Challenging Free Body Diagram Problem (Statics)

1. Homework Statement Given the picture, find theta, and the magnitude of the force going from point A to B. I have asked multiple people how to solve this problem and they have no idea, I end up getting 2 equations with 2 unknowns but then when I try to solve for theta I get 70cos(theta) -...
50. ### How do I draw a free body diagram of a car on a slope?

Homework Statement A car attempts to accelerate up a hill at an angle θ to the horizontal. The coefficient of static friction between the tires and the hill is µ > tan θ. What is the maximum acceleration the car can achieve (in the direction upwards along the hill)? Neglect the rotational...