Attn: Jose Reyes : the next you’re given grief by a member of the broadcasting community for risking a broken collarbone on a head-first slide, be sure to have the following item bookmarked. David A. Peters, Ph.D., the McDonnell Douglas Professor of Engineering at Washington University in St. Louis, is standing up for your right to leave your feet. From Washington University’s Tony Fitzpatrick (link courtesy David Williams):
Peters is a mechanical engineer who specializes in aircraft and helicopter engineering. He sees “fields of dreams” a bit differently than most ” he sees them as playgrounds of math and physics.
Peters says that dynamics equations can determine which slide gets you there more quickly, and that there are three important mathematical issues at play.
“There’s momentum ” mass of the body times how fast the player is moving,” he says. “There’s angular momentum (mass movement of inertia times the rotational rate). If it’s feet-first and you’re starting to slide, your feet are going out from you and you’re rotating clockwise; if it’s head-first, as your hands go down, you’re rotating counterclockwise.”
“On top of this is Newton’s Law,” Peters explains. “Force is mass times acceleration. Then moments of inertia times your angular acceleration.”
So, who gets there faster?
“It turns out your center of gravity is where the momentum is,” Peters says. “This is found half way from the tips of your fingers to the tips of your toes. In the headfirst slide, the center of gravity is lower than halfway between your feet and hands, so your feet don’t get there as fast. It’s faster head-first.”