Skateboarders rock physics

Experienced riders show gut knowledge of slope speeds

SEATTLE — Skateboard freaks know some righteous physics, dude. That’s because their hair-raising rides provide body-based insights into slope speeds that often elude those without a need for thrills and spills.

A ball travels faster down a relatively long incline that angles steeply downward in two sections separated by a flat stretch compared with a shorter incline that angles downward modestly but without changing slope.