Free Body Diagrams with Animated GIF Files - Abstract

Oct 25, 2026

Uploaded by Dusta123

A free body diagram (FBD) removes connecting bodies so only the forces acting on a selected body remain visible. Correct FBD construction enables mechanical engineers and students to write equilibrium equations that solve for unknown forces and moments. The paper addresses common learning difficulties by supplying step-by-step instructional examples delivered through animated GIF files, suitable for use in classroom PowerPoint and supported by screenshot-based explanation of their creation process.

LanguageEnglish

CategoryTechnology

FormatPDF

Pages12

Reading Time30 min

AccessFree to download

Free Body Diagrams with Animated GIF Files

Abstract

Free body diagrams of mechanical systems

FBD in a gear train

Steps for drawing a gear train FBD

Paper ID \#16401 Free Body Diagrams with Animated GIF Files Dr. Shih-Liang Wang P.E., North Carolina A&T State University Shih-Liang (Sid) Wang is Professor of Mechanical Engineering at North Carolina A&T State University. 􀀍c American Society for Engineering Education, 2016 Free Body Diagrams with Animated GIF Abstract A free body diagram (FBD) is a graphic representation in which all connecting bodies have been removed, or the body is “freed” from connecting bodies, to shows all forces acting on the body. Drawing a FBD is important in force analysis as it facilitates writing equations of equilibrium of a mechanical system to determine unknown forces and moments. Drawing a FBD correctly is thus an important skill for an engineering student. Many students have troubles drawing FBDs as there are insufficient examples in the textbooks, especially in the junior and senior level design courses. Over the years, the author has created many FBDs to assist students’ learning. In this paper, the author presents several examples using animated GIF files to guide students to develop FBDs step by step, and these animated GIF files can be easily incorporated in a PowerPoint presentation. Because animation will only work on a computer, screen shots of these animation files are shown in this paper, and the process of creating them is explained. Keywords Free body diagram (FBD), machine design, statics, and animated GIF. Free body diagrams of mechanical systems A free body diagram (FBD) is a graphic representation of a body (element or segment of an element, sub-assembly, or assembly) in which all connecting bodies have been removed, or the body is “freed” from connecting bodies, to shows all forces acting on the body. Drawing a free body diagram can help determine equations of equilibrium of the body in statics to solve for unknown forces and moments. Textbooks in design of machine elements 1,2,3 provide limited examples in FBDs on gears, shafts, bearings, power screws, bolted joints, and others. One of the reasons for lack of helpful examples is that it is cumbersome to construct a complex FBD with a CAD (Computer Aided Design) software package in the past. With the advancement of CAD, the task to draw FBDs becomes manageable to instructors. Since the effort can be reused semester after semester, these FBDs become very useful in classroom teaching, as more FBDs are being been created. To help students understand the steps to develop FBDs, the author has used step-by-step figures to show the process of constructing a FBD, and these figures have led to animated GIF files for animated FBDs. Animated GIF files are easy to produce4, as they are basically stop motion animations consisting of separate figures. Animated GIF files better than other types of animation, as they are small in file size and are easy to be incorporated in PowerPoint slides and web pages. The first example in this paper is the FBD ofa gear train. FBDs are used to solve unknowns progressively from the input gear, idler pair, and finally the output gear. The animation is intended to show the progression of drawing these related FBDs. The second example is the FBD of a bolted joint. This example is intended to show the relation between internal forces on the bolt, nut, and clamped members: the tension on the bolt and the compression on the clamped members are equal and opposite. The next two examples (a c-clamp and a vise grip) are to illustrate the FBD ofa power screw which transmits axial force and torque. The last example is ofa bevel gear on a shaft to show FBDs in assisting drawing shear force and bending moment diagrams. Finding the maximum moment along a shaft is important to identify the critical point of the shaft for the maximum stress. However, many students have trouble drawing these diagrams. This animated FBD is intended to help student understand the process by showing the progression from one end of the shaft to the other end.

FAQs

What is a free body diagram (FBD) and why is it important?

An FBD is a graphic model where connecting bodies are removed so only forces acting on a body are shown. It supports equilibrium analysis to determine unknown forces and moments.

Why do many students have trouble drawing FBDs?

Students face limited examples in design-machine-element textbooks, especially in junior and senior design courses. Creating complex FBDs with CAD tools was also historically cumbersome.

How do animated GIF files help students learn to construct FBDs?

The paper uses step-by-step animated GIFs to show the progression of drawing related FBDs. The files are small, work on computers, and can be inserted into PowerPoint slides and web pages.

Oct 25, 2026

Uploaded by Dusta123