RESEARCH ON PARAMETERS RELATED TO PROJECTILE VELOCITY IN “RULER-CANNON” SYSTEMS

The “ruler cannon” is a mechanical device consisting of two closely placed rulers and a cylindrical projectile inserted between them; when a force is applied, the projectile can be ejected at high speed. The process involves complex changes such as energy conversion, strain energy, and frictional dissipation. This paper aims to systematically investigate the key parameters affecting the ejection velocity of the projectile and their underlying mechanisms. Based on the Euler-Bernoulli beam model, a theoretical model describing the ejection velocity is established. An integrated experimental platform with “constant-force generation, symmetric loading, and real-time force measurement” is independently constructed, and quantitative studies on the magnitude of the external force, projectile radius, and ruler length are conducted through controlled-variable experiments. The results show that, within the experimental parameter range, the ejection velocity is positively correlated with the external force and projectile radius, while it first decreases and then increases with increasing ruler length, exhibiting a distinct minimum point. The study also reveals the critical ejection conditions and the applicability limits of the model. This work not only deepens the understanding of the energy conversion and dissipation mechanisms in the “ruler cannon” system, but also provides theoretical and experimental references for the analysis and optimization of similar elastic-friction coupled mechanical systems.