Feb 17th, 2021 — Physics

Tale of Two Technologies: Conservation of Momentum

Time and time again, educators have blown us away with the creativity and innovation they bring to core demonstrations in physics. In his recent article, “Conservation of Momentum with Dual Technologies,” published in the February edition of The Physics Teacher, UK-based physics educator, Alan Bates, shared his take on conservation of momentum, combining a PASCO Smart Cart and an Arduino Microcontroller to create a mobile rubber band launcher that makes for an amazing demonstration and experiment. 

Bates’ mobile rubber band launcher uses a PASCO Smart Cart, an Arduino Microcontroller, a servo motor, and a home-made launcher consisting of a wooden stick, a nail and a rubber band. The complete apparatus enables students to observe the conservation of momentum as the rubber band is launched in one direction, causing the cart to recoil in the opposite direction.

Not only is this apparatus knock-your-socks-off-cool, but it also allows students to determine the initial kinetic energy for the launched rubber band and the total energy transferred by the system. By adding masses to the cart after every three recoil measurements, Bates’ was able to relate velocity data from the Smart Cart’s recoils to changes in mass. He then used this information, along with calculations of the total momentum of the system before and after a launch, to determine the total kinetic energy of the system, the elastic potential energy, and the efficiency of the conversion from elastic potential energy to kinetic energy in each trial. After completing his analysis of the system, Bates’ reported that the experiment, “verifies that elastic potential energy is not only transferred into kinetic energy but also other types of energy that include thermal and sound energy.” It's safe to say, Mr. Bates has blown us away with his creative and analytically powerful approach to the law of conservation of momentum. A complete review of his methods and analyses can be found in the February edition of The Physics Teacher.