Gravity train of variable mass


  • Yuji Kajiyama Gifu Shotoku Gakuen University



Gravity train, Gravity tunnel, variable mass system


The gravity train is a virtual vehicle that travels in a tunnel across Earth, and its motion due to only gravity is a simple harmonic oscillator. It can run at a constant velocity by appropriately exhausting fuel. In this case, the train obeys the equation of motion for a variable mass system. We discuss the mass and energy reduction of the gravity train during travel and find the optimal conditions for economical travel. This study is suitable for university students in physics classes.


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How to Cite

Y. Kajiyama, “Gravity train of variable mass”, Rev. Mex. Fis. E, vol. 21, no. 2 Jul-Dec, pp. 020213 1–, Jul. 2024.