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Design of Elasticity Coefficient Apparatus Based on Measuring Time of Photodiode and Vibration Sensor Jurusan Fisika FMIPA Universitas Riau Abstract Collision events are very often encountered in everyday life, one of which is a falling ball. The ball collides with the reflecting plane at a slower speed than when it fell and in the opposite direction. The speed ratio of the ball after and before the collision is known as the coefficient of restitution (e) which describes the elasticity of the collision and affects the ball^s bounce height, bounce time, and bounce duration. This study aims to design a collision experiment apparatus that can investigate the ball^s bounce height, bounce time, and bounce duration used to determine the coefficient of restitution. A prototype is made of a PVC cylinder with a diameter of 110 mm and 100 cm in height, which is then perforated on the wall surface to minimize the air friction in the tube. The prototype stand is equipped with a tray to replace the reflective material, while two photodiode sensors are installed on the tube with a reflective system to detect the light reflection on the falling object. To validate the time measurement, a vibration sensor is mounted on the floor which detects the bouncing ball. The apparatus is activated through an actuator that simultaneously turns on all sensors to produce accurate measurements. When the test object is dropped, the timer starts counting as the object passes through the first and second photodiode sensor, and also when it hits the floor. The results show that the restitution coefficient of the ball in various reflecting planes is agreed with the theory (0 ≤- e ≤- 1) and e is positive linear with the bounce height (h), the time of each bounce (t), and the duration of the bounce (ttotal). Keywords: Collision- straight line- coefficient of restitution- photodiode sensors- vibration sensor Topic: System and Applications |
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