SPRECIAL FOCUS PAPER A FLEXIBLE ONLINE APPARATUS FOR PROJECTILE LAUNCH EXPERIMENTS A Flexible Online Apparatus for Projectile Launch Experiments http://dx.doi.org/10.3991/ijoe.v9iS1.2289 Carlos Paiva, Pedro Nogueira, Gustavo Alves, Arcelina Marques, Pedro Guimarães, Rubem Couto 2 Polytechnic of Porto, Porto, Portugal Abstract—In order to provide a more flexible learning environment in physics, the developed projectile launch apparatus enables students to determine the acceleration of gravity and the dependence of a set of parameters in the projectile movement. This apparatus is remotely operated and accessed via web, by first scheduling an access time slot. This machine has a number of configuration parameters that support different learning scenarios with different complexities. Index Terms—Remote Experiment, projectile launch. I. INTRODUCTION Distance education has been in use for several years at the Polytechnic of Porto – School of Engineering (ISEP), but the application of remote laboratories in physics was exclusively being used in the electric and electronic fields. For that purpose, VISIR [1, 2] and Remote ElectLab [3] supported remote experiments in electronics. The need for a similar approach supporting other experiments in Physics has led us to develop a machine able to perform projectile launch experiments remotely. This type of apparatus, supporting different complexity levels on the projectile movement characterization, can be used to address several topics on a typical physics curriculum, under different learning scenarios. A similar approach with a free body fall apparatus to achieve gravity acceleration determination has been developed by Martin Connors and described in [4]. II. APPARATUS LAYOUT This apparatus is a self-contained box that requires a power plug and an Ethernet connection. The box has an internal web server accessible through a SCORM- compliant scheduler. This server also enables a local mode for use in exhibitions and demonstrations. The apparatus is shown in Fig.1 and is divided in four sub-assemblies: A. Ball Selector Selects one out of three balls with diameters ranging from 14 mm to 18 mm, allowing the study of mass (non-) influence on projectile motion. B. Main Elevator Executes three operations in the process. Firstly, it loads the ball by moving to its lower limit loading position. Then it lifts-up the ball to a position leveled with the ramp. If the ramp is on place it will move up for a few millimeters to mechanically launch the ball to a zone where an electromagnet placed on the ramp will collect it. Figure 1. Apparatus side view C. Ramp Elevator Ramp Elevator has two main purposes: user setup angle and user setup height. The ramp angle can range from -20º to +20º. The launch height can be set up to 380 mm above touch down plane. Switching off the electromagnet triggers the ball movement down the ramp. D. Ball Collector (landing zone) Works by gravity and its main purpose is to collect the launched ball back to the ball selector. This assembly also contains the projectile horizontal range measuring system. This is an optical system based on a reflective infrared light barrier. The impact point measurement is obtained by interrupting a set of photo-detectors, 2 mm apart. III. WEB INTERFACE The web interface (Fig. 2) allows users to setup their experiment and receive the experimental data. It also provides the user with a live video stream of the whole process, captured by a webcam. Together with the experimental data, a photo taken at the moment the ball touches the landing zone is also sent via the user interface. The purpose of this photo is to allow users to make the actual measurement of the maximum horizontal displacement in order to compute the projectile range. All data is available for inspection via the user interface. iJOE – Volume 9, Special Issue 1: "REV2012 Exhibition", January 2013 35