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Classroom Models For Illustrating Dynamics Principles Part Ii. Rigid Body Kinematics And Kinetics
| Content Provider | Semantic Scholar |
|---|---|
| Author | Magill, Michael A. |
| Copyright Year | 1997 |
| Abstract | This paper is part II in a two part series that describes a collection of ten classroom models used to illustrate basic Dynamics principles. The models discussed in part I of the series cover the topics of Particle Kinematics and Kinetics while part II covers Rigid Body Kinematics and Kinetics. These models are excellent tools for communicating basic Engineering Mechanics concepts while also stimulating interest and enthusiasm. These devices were developed for undergraduate engineering technology students but they are equally valuable for engineering students. Most of these models are inexpensive or can be constructed easily. INTRODUCTION Dynamics is one of the more difficult courses that engineering and engineering technology students encounter during their undergraduate study. As a result, mechanics instructors are trying continually to find or develop techniques that enhance student learning. One of the greatest challenges is creating student interest and enthusiasm. It is well known that students learn more and work harder when they are interested in a topic. A good technique for breaking the monotony of classroom lectures and creating student interest is to introduce exciting classroom models. These models teach basic mechanics principles but more importantly they get students involved, stimulate interest and give a change of pace. The time required to properly present a model is roughly the same as presenting an example problem. THE CLASSROOM MODELS The models discussed in this paper (Part II) cover the topics of Rigid Body Kinematics and Kinetics. All the information necessary for developing these models and presenting them in the classroom is provided within the paper. The details for each model are provided on separate pages to facilitate duplicating and using them as classroom handouts. The description of each model includes an interesting problem statement, descriptive diagrams, and the analytical solution. The five classroom models* presented in this paper are: • Equation of Motion Rolling Yo-Yo • Equation of Motion Rolling Ring Versus Rolling Disk • Mass Moment of Inertia Rolling Solid Cylinder Versus Rolling Hollow Cylinder • Work/Energy Weight Suspended From a Wheel • Conservation of Momentum Rotating Bicycle Wheel P ge 202.1 PROCEDURE/APPROACH The approach used for presenting these models will control their ability to stimulate interest and communicate mechanics principles. Just showing the model and throwing the analytical solution on the overhead will not produce the desired results. The following is an outlined approach that the author has found to be successful. • Start by introducing the model and posing one or two interesting questions. • Ask for a show of hands on each of the possible solutions. Establish a competitive spirit in the classroom. Have a couple students offer a solution using their “gut feeling.” • The next step is to lead the students through the analytical solution. This phase should be performed quickly without covering a lot of detail. Too much detail at this point will distract the students and they may lose interest. This phase moves more efficiently and is more effective if copies of the analytical solution are distributed and also shown on the overhead. This phase of reviewing the analytical solution can include the following: • Determine if the problem requires a particle or rigid body solution. (i.e., Is the body rotating? Is the body’s size of consequence? Make a clear distinction between rotation and curvilinear motion.) • Determine if the problem requires a kinematic or kinetic solution or both. (i.e., Does this problem involve a force analysis or just motion geometry?) • If the solution requires a kinetic solution determine which procedure is best. • Establish the proper diagrams. • Set up the basic governing equation(s). • Obtain one or two volunteers to assist with demonstrating the model. Make the demonstration fun and interesting. • Return to the analytical solution to clear up details and ask additional questions. This is also a good time to discuss the validity of any assumptions. There are many creative techniques for using models. Try having students present the models. Better yet, have each student develop a model and then present it and the analytical solution to the class. The best student models can be saved for future semesters. CONCLUSION The key to making these models successful is making them fun and interesting. Models are excellent tools for communicating basic Engineering Mechanics concepts while also stimulating interest and enthusiasm. MICHAEL MAGILL is an Associate Professor in Mechanical Engineering Technology at Purdue University. Prior to joining Purdue University he was on the faculty at Oklahoma State University for eleven years. Professor Magill’s areas of interest are solid mechanics, applied structural analysis and computer-aided analysis. He has a B.S. and M.S. in Mechanical Engineering and a Ph.D. in Civil Engineering, all from Oklahoma State University. *The ideas for these models came from various sources so the author does not claim ownership or copyright. P ge 202.2 RIGID BODY: EQUATION OF MOTION ROLLING YO-YO Supplies: Yo-yo. Given: r1 = yo-yo center peg radius r2 = yo-yo radius m = yo-yo mass T = constant string tension Assume no slipping! (a) (b) Find: Which way will yo-yo roll? Solution: a) Assume yo-yo moves to the right so maG must be to the right and Ff to the left to force rolling. FBD KD ΣFx = T − Ff = maG ← T must be greater than Ff or maG will be to the left. T − Ff = mαr2 ← aG = αr2 because there is no slipping. α = − T F m r f 2 ← ∴Positive, so correct direction assumed!! T T |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | https://peer.asee.org/classroom-models-for-illustrating-dynamics-principles-part-ii-rigid-body-kinematics-and-kinetics.pdf |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
