Physics
Free Body Diagrams
Free body diagrams are visual representations used to analyze forces acting on an object. They isolate the object of interest and show all the forces acting on it, including magnitude, direction, and type. By using free body diagrams, physicists can better understand the forces at play in a given situation and make predictions about the object's motion.
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4 Key excerpts on "Free Body Diagrams"
- Robert Jansen, Greg Young, Barron's Educational Series(Authors)
- 2022(Publication Date)
- Barrons Educational Services(Publisher)
x is the distance the spring is either stretched or compressed (units: m). Every spring has its own unique spring constant. Finding the spring constant, if it is not given, is often the first critical step in solving spring problems.Force DiagramsThe first step in solving a dynamics problem is to identify all forces, including the direction of each force, acting on an object. This can be accomplished by constructing a force diagram, known as a free-body diagram. A free-body diagram includes only the object and the forces acting on the object. It is free of clutter and does not include surfaces, strings, springs, or any other agents acting on the object. A free-body diagram serves two key purposes: First, it allows you to visualize how the forces will influence the motion. Second, it provides a frame of reference in which to work with the force vectors.EXAMPLE 5.1Free-Body Diagrams A 10-kilogram mass is pulled at constant velocity to the right along a rough horizontal surface by a string. Construct a free-body diagram depicting all the forces acting on the mass. WHAT’S THE TRICK? Identify all the forces acting on the mass.•Gravity is not mentioned in the problem. Unless specified otherwise, problems take place on Earth, so the force of gravity, Fg , is present.•You may be able to deduce some forces from the diagram. Both a string and a surface are in contact with the object. Therefore, tension, T, and the normal force, N, are present.•Identifying other forces requires you to read the text of the problem. This problem mentions a “rough” surface, implying that friction, f, is present.The resulting free-body diagram is shown below left. Free-body diagrams are nearly identical to plotting vectors on coordinate axes, as shown below right.
eBook - PDFEngineering Mechanics: Statics
Modeling and Analyzing Systems in Equilibrium
- Sheri D. Sheppard, Thalia Anagnos, Sarah L. Billington(Authors)
- 2017(Publication Date)
- Wiley(Publisher)
195 C H A P T E R 4 ◆ he free-body diagram is the most impor- tant tool in this text. It is a drawing of a system and the loads acting on it. A four- step process is used to create a free-body diagram. First, you mentally separate the sys- tem (the portion of the world you are inter- ested in) from its surroundings (the rest of the world). Second, you draw a simplified representation of your system, noting any assumptions you have made when creating your drawing. Third, you identify all the known loads (forces and moments) acting on the system and add them to the drawing. Finally, you draw the unknown loads acting on the system at the supports or other boundaries. This chapter is devoted exclusively to the task of creating free-body diagrams. We build on the coverage of forces (Chapter 2) and moments (Chapter 3) and on the engineering analysis procedure pre- sented in Chapter 1. In Chapter 5 you will learn how to solve for unknown loads in your free-body diagrams. FOUR STEPS TO CREATING A FREE-BODY DIAGRAM 1 Study the physical situation 2 Draw system; state assumptions 3 Draw known loads 4 Identify and draw support loads T Hazlan Abdul Hakim/Getty Images W P F 3 F 3 F 1 N 3 N 3 N 1 N 4 N 4 F 4 F 4 F 2 N 2 y x W E N 1 N 2 F 1 F x F 2 F y M z MODELING SYSTEMS WITH FREE-BODY DIAGRAMS 196 CH 4 MODELING SYSTEMS WITH FREE-BODY DIAGRAMS L E A R N I N G O B J E C T I V E S ◆ On completion of this chapter, you will be able to: ◆ Describe how external loads, including distributed loads, are depicted on free-body diagrams. (4.1) ◆ Identify the standard supports for planar systems and how they are represented on a free-body diagram. (4.2) ◆ Identify the standard supports for nonplanar systems and how they are represented on a free-body diagram. (4.3) ◆ Determine by inspection whether a system should be modeled as planar or nonplanar. (4.4) ◆ Apply a step-by-step approach to creating free-body diagrams of various systems.
eBook - ePubAnalysis of Structures
An Introduction Including Numerical Methods
- Joe G. Eisley, Antony M. Waas(Authors)
- 2011(Publication Date)
- Wiley(Publisher)
In the case of a statically indeterminate body we must introduce additional equations to obtain a solution. In this chapter we shall be interested primarily in statically determinate bodies. The subsequent chapters will contend with both statically determinate and statically indeterminate problems.2.2 Free Body DiagramsWe shall illustrate each subcase with a simple example in two dimensions using concentrated forces only. In these examples it is assumed that the applied forces initially are known and the restraint forces are unknown.Consider the rigid body shown in Figure 2.2.1 . We introduce some common symbols to illustrate forces and restraints. For now we consider only concentrated loads and, in this case, assume they act entirely in the xy plane. We add concentrated restraints. The restraint on the lower left prevents movement in both the x and y directions but does allow rotation about the z axis. The restraint on the lower right prevents movement only in the y direction, since it is assumed to roll freely (without friction) in the x direction. Since it is assumed that there are no forces in the z direction there is no need to consider restraints in the z direction.Figure 2.2.1By replacing the restraint symbols in Figure 2.2.1 with visual representations of the characteristics to which we have assigned them, we create what is called a free body diagram. We draw the free body in Figure 2.2.2 showing all the applied forces and restraint forces. Unless otherwise stated we shall use the symbol F for concentrated applied forces and R for concentrated restraint forces. Appropriate subscripts will be added to identify individual forces and components. It is common to represent both the applied forces and the restraint forces in terms of their components in the appropriate coordinate directions. For the applied forces these components are(2.2.1)Figure 2.2.2According to standard sign convention, restraint force components generally are drawn directed along the positive x and y
eBook - ePubIntroductory Physics
Summaries, Examples, and Practice Problems
- Michael Antosh(Author)
- 2023(Publication Date)
- CRC Press(Publisher)
Specific Types of Forces, and Force ProblemsDOI: 10.1201/9781003005049-55.1 Introduction: There are Different Types of Forces
There are many different types of forces in the world. In this chapter, we’ll look at the types of forces that are most commonly discussed in introductory physics courses, as well as looking at three specific types of force problems. But before that, we need to talk about the very useful topic of Free Body Diagrams.5.2 Free Body Diagrams
A free body diagram is a very useful tool to help you do physics problems. For each object in a given problem, making a free body diagram is as simple as this:- Draw something to represent each object in the problem. Usually there is only one object; occasionally there are two or three in a complicated problem. Tipler’s text (cited in the acknowledgements) suggests using just a dot instead of drawing a full picture.
- Set a coordinate system, similar to what we talked about earlier in the textbook, for example in Chapters 2 and 3 . For each dimension (likely two dimensions, but possibly one for specific problems), have a positive direction. Most often, “to the right” or “east” can be positive x, and “up” or “north” can be positive y.
- Spend some time thinking about what forces are on the object. For every force that you think is on the object, draw that force. Label it with the amount of force (magnitude), and draw it in the direction it is going.
- Sometimes you may not know the magnitude or direction of a force; in that case you can give that force two components (one in the + x direction and one in the +y direction) and figure out later what those forces are.
Once a correct free body diagram is made, it’s easy to add up the forces in the x and y directions. Remember from Chapter 4
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