Abstract: All first year Biomedical Engineering students are required to complete the Vacation Design (ELEN1997) course. The course consists of one project, which is to be completed during the December-January vacation. The project requires students to design, build, calibrate and test a device that shoots a Ping-Pong ball. The Ping-Pong ball must land at any given distance within the range of 3 to 6 meters. The device designed is powered by the extension of two springs, and shoots a Ping-Pong ball through a PVC pipe, which acts as a barrel. Calibration was achieved by altering the extension of the springs. The method of testing involved selecting a particular extension level and then repeatedly firing the device until consistent results were
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According to the principle of Work and Energy [6], kinetic energy equals the work of a spring force, or
To collect experimental data, an arbitrary value of extension was selected, and the catapult was shot at that extension level until 5 results were achieved within 50cm of each other. Those results were then averaged, and the average was taken as the horizontal range for that extension. This procedure was then repeated until all distances between 3 and 6 meters had been covered. Taking the average value as the range for that extension means that an accuracy of ±25cm is achieved for all extension levels.
There are large inconsistencies between the calculated values and the experimentally determined values, as the range of the calculated data (from 0m to 26.8m) far exceeds the range of the experimentally determined data (from 0m to 6.2m). There are many reasons for these discrepancies. Firstly, the value for air density was taken at ‘20°C’ [7]; however the air temperature was not 20°C at the time of testing. This inconsistency affects the value of terminal velocity and thus, of the
According to the principle of Work and Energy [6], kinetic energy equals the work of a spring force, or
To collect experimental data, an arbitrary value of extension was selected, and the catapult was shot at that extension level until 5 results were achieved within 50cm of each other. Those results were then averaged, and the average was taken as the horizontal range for that extension. This procedure was then repeated until all distances between 3 and 6 meters had been covered. Taking the average value as the range for that extension means that an accuracy of ±25cm is achieved for all extension levels.
There are large inconsistencies between the calculated values and the experimentally determined values, as the range of the calculated data (from 0m to 26.8m) far exceeds the range of the experimentally determined data (from 0m to 6.2m). There are many reasons for these discrepancies. Firstly, the value for air density was taken at ‘20°C’ [7]; however the air temperature was not 20°C at the time of testing. This inconsistency affects the value of terminal velocity and thus, of the