Here in the US, the baseball playoffs will begin today. And as someone who is living in Chicago and only 2 blocks away from Wrigleyfield, I can certainly not ignore such an event even if I tried, especially with both the White Sox and the Cubs in contention.
So it is very timely that we talk a little bit about one aspect of the physics of baseball - the slid into base. The question here is, which one will be faster: a head first slide, or a feet first slide? A Washington University physicist David Peters says that a headfirst slide is faster.
According to Peters, it's simple physics: As a runner slides headfirst, the body's center of gravity -- and therefore its momentum -- is thrust forwards. Slide feet first, and the body's center of gravity falls backwards, away from the base.
"It's basic, fundamental angular momentum and Newton's laws applied to a body in motion being flung through the air," Peters said. Fellow physicist Alan Nathan agreed, noting that it's easier for a runner's churning legs to generate force with head and arms leading, not trailing.
If you read the rest of the article, it points out that there's not a lot of convincing empirical evidence supporting either sliding technique, mainly because this hasn't been done in a controlled manner. Still, from my uneducated guess, I also think that a headfirst slide is faster. But is this worth doing at the risk of a higher probability of injury?