Feld and McNair found that beginning students can throw a karate chop at about 20 feet per second, just enough to break a one-inch board. But
a black belt like McNair could chop at 46 feet per second. Hitting a piece of wood at that speed, a 11/2-pound hand can deliver a wallop of up to 2,800 newtons (one newton is roughly equal to the force exerted by the weight of an apple). Splitting a typical concrete slab 11/2 inches thick actually takes less, about 1,900 newtons. Of course, brute strength is not the only requirement for breaking concrete blocks — the nature of the chop is also important. Karate students must learn that for a strike to have maximum momentum, it must have a follow-through; golf and tennis players follow through with their swings for the same reason.