# Steve Vogel : Lifes Launchers: The Scaling of Bioballistic Projectiles

Biological projectiles range from a 10-micrometer spore to a 1-meter leaping mammal. Pre-launch accelerations scale inversely with length, with that of the smallest projectile approaching a million times gravity. These projectiles follow Borelli's rule, that all jumpers should jump to the same height. Nonetheless, his rationale is wrong on at least two accounts. For one thing, it presumes a muscular engine operating with no energy storage, often far from the case. For another, it ignores drag, critical for small projectiles, which operate in an overwhelmingly drag-dominated rather than gravity- dominated domain and whose optimal trajectories look decidedly unfamiliar. But the rule can be given quite a differentÂ?and more generalÂ?basis. And a simple dimensionless index helps us anticipate best launch angles and path lengths, these latter illustrated with a simple computer simulation.

**Category**: Mathematical Biology**Duration**: 59:54**Date**: May 18, 2011 at 8:55 AM**Views**: 117-
**Tags:**seminar, Mathematical Biology Seminar

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