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. R

    What is a free body diagram and how can it be used to analyze forces on a body?

    Hi i just wanted to know if anyone can help me located a system diagram with atleast 5+ forces acting on it? P.S. the diagram it self should be in rest position.
  2. 7

    How Does Static Friction Affect Bicycle Acceleration?

    Homework Statement Consider a biker riding on level ground as shown. She wants to have the maximum forward acceleration possible, which means experiencing the maximum horizontal force without her wheels slipping. Draw the free body diagram for the bike accelerating forward. Homework...
  3. X

    Deriving an equation through a free body diagram

    Homework Statement Use a Free body diagram to show that :Tanθ=static friction, on an incline plane Homework Equations FF/FN= coeficiant of friction The Attempt at a Solution I know I must get an angle to have a tan of the Force of friction and a Normal force, but I don't...
  4. S

    How can torque be used to solve for tension in an extended free body diagram?

    Homework Statement I need help with this: http://img716.imageshack.us/img716/3262/unledewk.jpg I know that I need to create an extended free body diagram and I understand how to get all the equations from the diagram. BUT I don't know what to do when it comes time to use torque and find...
  5. A

    Free Body Diagram Of a Situation

    Homework Statement Hello people, First of all, this is my first day in this forum and this post is my very first post. So, I am extremely sorry if I violate any rules here. I have to solve a problem involving frictions. I will solve the problem myself; I just need help with drawing the Free...
  6. N

    Calculating Vertical Forces in a Cantilever Beam Setup

    Homework Statement This is not a homework problem, but something i can't figure out how to calculate. Basically I have what is similar to a cantilever beam setup with an extension. what i need to figure out is what the vertical forces are at the two points(triangles on the attached paint...
  7. A

    What should be the free body diagram?

    Homework Statement The Question gives some data, and a figure to find out the acceleration. In the arrangement shown (refer attachment) shown, M1=20kg, M2=30Kg, floor is smooth and friction between two blocks: μ(s) = 0.6, μ(k) = 0.4. F= 400N What are the forces acting on the two blocks...
  8. T

    Analaysis Forces on Free Body Diagram

    So, I have created some blocks, and draw the FBD myself, am not sure if I did it right or not, so I'm going to upload these FBD here, and hope you guys can correct me if I'm wrong. Thanks a lot. A block of m1 and m2, m2 is siting on top of m1. Assume there is no friction on the ground under m1...
  9. T

    Force and motion in Newton's laws and free body diagram

    A 40 kg girl and an 8.4 kg sled are on the frictionless ice of a frozen lake, 15 m apart but connected by a roped of negligible mass. The girl exerts a horizontal 5.2N force on the rope. What are the acceleration magnitudes of (a) the sled (b) the girl (c) how far from the girl's initial...
  10. J

    Understanding centripetal force and free body diagram

    Homework Statement a person is standing stationairy on Earth (whilst it is rotating) there is a net force towards the centre of the earth. What would the free body diagram look like. Please could someone explain why thanks Homework Equations I know the formula for...
  11. M

    Need Help Creating a Free Body Diagram of a Car on a Slope

    Hello. I have attached an image of a free body diagram of a car traveling up a ramp at 30 degrees. I was wondering if anyone can help me determine the sumation of forces in the X and Y direction. I understand that the forces in the Y-direction must be equal to zero or else the car will not...
  12. S

    Free body diagram of atwood machine

    Homework Statement I need to find the forces on this modified atwood machine: http://imageshack.us/photo/my-images/36/atwood.jpg/ The Attempt at a Solution What I think: - On mass M there are two forces, Mg and -T. - On the mass above the spring there are two more forces, -2mg...
  13. Femme_physics

    Engineers view of the world - Free Body Diagram

    Okay, I'm still working on it... but this is a free body diagram of the front of my college's view from a nearby park, which I have special feelings too. It's the place that introduced me to the beauty and majesty of physics, and first place that showed me that I am able to be an excelling...
  14. G

    Situation diagram and free body diagram

    Hi all, What is the difference between a situation diagram and free body diagram? I understand what a free body diagram is. Thanks.
  15. P

    Why is kinetic friction always lower than maximum static friction?

    I was reading about those in my textbook and they drew an example of a block resting on a ramp. The diagram showed the force of friction. How is there friction if the block is not moving? Thanks, Peter G.
  16. J

    Free body diagram for hinged rods

    Hello all! First post! I've been meaning to join this board for a while. I'm an electronic engineer with interests in physics. I set myself the challenge of trying to obtain the dynamics equations for a double pendulum setup without using Lagrange. (configuration in attached picture)...
  17. Femme_physics

    Brakes, static equilibrium problem is my Free Body Diagram correct?

    Homework Statement Calculate minimal force P of the brakes during the stopping of the wheel. http://img823.imageshack.us/img823/6017/problemzy.jpg Solution is P=34.3 [N] Homework Equations (Written on scan above) The Attempt at a Solution...
  18. K

    Free body diagram, bearing forces

    Hi, I wish to work out the reaction forces on the following diagram: [PLAIN]http://img227.imageshack.us/img227/7055/imag0211b.jpg The circle is a gear with tangential force acting at Ft and radial force acting at Fr. A and B are bearings that take the Ft and Fr forces. I have...
  19. S

    Drawing a free body diagram for vectors

    I have some question related to vectors. 1)How will you find a vector(A) if you given another vector(B) in +x-direction to give a resultant(R) at θ(any degree)? 2)A child is holding a wagon from rolling straight back down a driveway that is inclined at 20° to horizontal. If the wagon...
  20. A

    Pulley Free Body Diagram and rope tension

    Homework Statement The figure above shows an 80 kilogram person standing on a 20 kilogram platform suspended by a rope passing over a stationary pulley that is free to rotate. The other end of the rope is held by the person. The masses of the rope and pulley are negligible. You may use g...
  21. 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...
  22. C

    Free body diagram, normal force, static friction

    Homework Statement There is a roller coaster cart with passengers sitting on the top of a 23 degree incline. The ride is about to start. The combined mass of the cart and passengers is 363kg. a) What would the free body diagram look like? b) How do you solve for normal force? c) How do...
  23. 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...
  24. 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...
  25. P

    Free body diagram for mass on oscillating spring

    Homework Statement What does the free body diagram look like for a mass on an oscillating spring, when the mass is at its midpoint. Homework Equations F=-kx The Attempt at a Solution I'm not sure how an oscillating spring FBD is different from one for a non-oscillating spring. I...
  26. S

    Free Body Diagram of Pulley with Friction

    Homework Statement Draw a freebody diagram of the fixed pulley used in your lab. I am trying to get ahead in my statics class so I can start preparing for finals, but we haven't covered this in class yet, and it is not in our textbook. Our lab section is a bit ahead of our lecture...
  27. 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?
  28. M

    Easy Free Body Diagram Question

    Whats wrong with my answer? I've tried just about everything, but its not accepting it. I've tried +N too, even though I think what I have in there should be right.
  29. D

    What are the key steps for drawing a mass-spring free body diagram?

    I am trying to get started on a problem. I have two masses M1 = M2 and three springs all with the same constant. The weights and springs are on a frictionless table and the outer springs are attached to walls Wall ~~~Mass~~~Mass~~~Wall How do I draw the free-body diagram? I am confused...
  30. 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...
  31. S

    Understanding the Magnitude of T in Free Body Forces

    I)State the magnitude of the horizontal component of T II)Calculate the magnitude of T That was the question but i don't know what the difference between the magnitude of the horizontal component of T and the magnitude of T is :( could someone shed some light on this? xD It's question 5...
  32. C

    Understanding Centripetal and Gravitational Forces in Orbital Motion

    I'm having some trouble understanding this (not a homework question by the way.) A satellite orbits the Earth with a certain angular velocity. Centripetal acceleration is directed radially inward. Acceleration due to gravity of the Earth is also directed radially inward. If I draw a free body...
  33. T

    What Forces Act on a Car Pushing a Block in Physics?

    Homework Statement A car pushes a block across the floor. (assume that it is moving from left to the right) Draw a free body diagram for the car showing: Force by block on car. Force of friction. Force of Gravity. Normal force. Homework Equations The Attempt at a Solution Normal force...
  34. 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...
  35. E

    What mistake did I make in my free body diagram for this physics test question?

    Hello all, I just received back a unit test on fields that I wrote two or so months ago (teacher marks really slowly). I did pretty well on it. There is one question that I lost marks on. It isn't terribly difficult, but my teacher hasn't shown us the correct answers yet and I want to confirm...
  36. T

    Free body diagram, Kinematic/Momentum/Work and Energy/Power-Analysis Help

    1. Homework Statement (Here is what I was told to do) Free body diagram Kinematic Analysis Momentum Analysis Work and Energy Analysis Power Analysis Written descriptions, one paragraph for the above elements will go on each page, My issue is that I looked up each...
  37. 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...
  38. 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...
  39. 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
  40. W

    Box on Box on Box free body diagram

    Okay, so say that I stack three boxes, one on top of another. There is friction between all surface, including the bottom box and the ground. If I apply a force to the center box only, is there any set of circumstances under which the top box will slip? I know that if the applied force is...
  41. O

    Surface element meniscus - free body diagram

    Consider the free body diagram of a surface element of a water - glass meniscus in a vacuum. Along the line normal to the surface, the water pressure acts towards the vacuum, and the direction of the surface tension 'curvature force' depends on whether the surface curves like a 'u' or like an...
  42. C

    Free body diagram with circular motion

    Homework Statement In a circular rotating room (think Gravitron), there are two blocks stacked against the wall and do not drop. Block A is touching block B, and block B is touching the wall. Homework Equations The Attempt at a Solution I know how to do this problem, but I am not...
  43. O

    Maximum altitude of a rocket in 2D motion and free body motion

    Homework Statement A rocket is launched at an angle of 53 above the horizontal with an initial speed of 75 m/s. It moves for 25s along it's initial line of motion with an overall acceleration of 25 m/22. At this time its engines fail and the rocket proceeds to move as a freebody. a) What...
  44. P

    Simple Free Body Force Diagram + Friction Question

    I just want to check if I am doing the right thing with this force diagram. Forgetting the force of friction for the moment, if I know that the body is accelerating at 6.34ms^-2 with a mass of 6000kg; and the opposing force of mgsin3 is 3077.4N, then would the I have to add that to the...
  45. J

    Forces Free Body Diagram & Finding μ

    Homework Statement See the diagram here: http://i47.photobucket.com/albums/f173/xallip/bar2-1.jpg Known quantities: L, Ff. a) Find the x and y components of A and B. b) μ is a known quantity; give an expression for A in this case.Homework Equations The Attempt at a Solution a) Rx = Ff N + Ry...
  46. M

    Free Body Diagram for Hanging Weight with Two Ropes | Tension Comparison

    Homework Statement Two ropes are connected to a steel cable that supports a hanging weight as shown in the figure. http://session.masteringphysics.com/problemAsset/1000050931/2/YF-05-59.jpg Draw a free-body diagram showing all of the forces acting at the knot that connects the two ropes to...
  47. 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...
  48. V

    Angular Acceleration and Flow Rate Relationship

    Hey guys, Thanks for all the replies. I ended up having the test for this subject and the question was a bit different to what I was expecting. I have attached an image similar to that of the test question. Basically the question asked to explain what would happen to the angular...
  49. N

    Kinematics - Statics - Free Body Diagram

    Homework Statement https://online-s.physics.uiuc.edu/cgi/courses/shell/common/showme.pl?courses/phys211/spring09/homework/11/two-beams/fig3a.gif Two identical uniform beams, each of mass "M" and length "L", are symmetrically set up against each other on a floor with which they have a...
  50. V

    Free Body Diagram Help for Counterweight Pivot Moment

    Hey guys, I have a counterweight that connects to an L-shaped link that pivots about a point. I need to work out the moment at the pin due to the counterweight, but I am stuck on the basics. The first free body diagram I drew assumes that the weight of the counterweight acts entirely...
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