BYOE: Experimental Demonstration of Simplifying a System of Parallel Forces

The purpose of this Bring Your Own Experiment (BYOE) session is to describe a low-cost and hands-on activity of simplifying systems of parallel forces for the engineering mechanics (Statics) course. One of the most fundamental concepts in Statics course is to reduce a system of forces to a force-couple system. As hands-on activity can reinforce a fundamental concept, a demonstration unit was prepared using digital weight scales, a transparent plexiglass sheet, weights, and leveling feet. A brief explanation of the demonstration is explained here in this abstract. The experimental demonstration shows a system of parallel forces reduced to an equivalent resultant force and the coordinates of its line of action. At first, three leveling feet are placed on top of the three digital scales. A transparent plexiglass sheet was then placed on top of the leveling feet. The readings of the scales due to the weight of the plexiglass were zeroed at this point. A marker was used to mark the points on top of the plexiglass, touching the leveling feet's top faces. Three different loads were then carefully laid on top of the marked points on the plexiglass. The corresponding reaction forces were measured using digital scales. The digital scale shows the reading in terms of grams but later converted into force. A ruler scale, measuring tape, or slide calipers were used to measure the coordinates of three different points where the loads were placed. The origin can be any point on top of the plexiglass. Here three loads represent a parallel system of forces F1,F2, and F3. This parallel force system is then reduced to a force-couple system R=∑F;MOR and the position vector, r, of the resultant force,R, were found by applying the following relation. MOR=rR=∑MOF After determining the position, r, of the resultant force, R, a load equivalent to the resultant force R=∑F was placed on that position and measured the resulting reaction forces on the digital scales. At this point, the corresponding reaction forces on the digital scales should be the same as the loads of F1, F2, and F3. The lowest percentage difference reported is 2.5%. The full manuscript will show a complete module for this experimental demonstration.