Development and Evaluation of an Arduino-Based Free-Fall Experiment Kit and Changes in Pre-Service Physics Teachers’ Conceptual Understanding

Abstract

Free-fall motion and gravitational acceleration are fundamental topics in mechanics; however, conventional laboratory activities are often affected by manual-timing uncertainty and may provide limited opportunities for learners to connect theoretical relationships with experimental evidence. This study aimed to develop an Arduino-based free-fall experiment kit, evaluate its scientific, technical, and instructional quality, and examine changes in pre-service physics teachers’ conceptual understanding after participating in the learning activities. The study employed a research-and-development process guided by the ADDIE framework, together with a pre-experimental one-group pretest–posttest implementation. There were 30 first- to third-year pre-service physics teachers selected through purposive sampling. The developed apparatus integrated an Arduino Uno R3, an HC-SR04 ultrasonic distance sensor, a servo-controlled release mechanism, and a liquid-crystal display. Three experts evaluated the quality and instructional suitability of the kit. Technical performance was examined through 10 repeated trials, and conceptual understanding was assessed using a 30-item multiple-choice test. The apparatus produced a mean gravitational acceleration of 9.26±0.19 m/s², with an average error of approximately 5.62% relative to the adopted reference value of 9.81 m/s². The expert evaluation yielded an overall rating at the highest level (M=4.70, SD=0.40). Based on the item-level percentages reported in the study, the mean correct-response percentage increased from 28.3% before learning to 78.0% after learning, representing an increase of 49.7 percentage points and a normalized gain of 0.69, moderate gain, close to the high-gain threshold . The findings suggest that the kit provided relatively consistent measurements and supported hands-on data collection and interpretation. Further calibration and controlled comparative studies are required before stronger conclusions regarding measurement accuracy and instructional effectiveness can be made.