CoachThe balance point of an object is the special spot where it can be held up level — as if all its weight gathered there. A ruler carries its balance point in the middle; a hammer hides it near the heavy head. Held right under its balance point, any object rests level on one finger.
示例
Example 13.10 (The acrobat’s pole)
Why does the tightrope walker carry that long, drooping pole? It is her balance helper: when she starts tipping to one side, the long pole makes the lean slow and lazy instead of quick, and gives her time to shift back over the rope. You use the same trick with bare arms when you walk along a curb — arms out, wobble slowed, balance saved.