[問題] 球轉速判斷
想請教版上各位大大
近年在看直播經常看到螢幕跑數據統計裡
開始出現一項“球的轉速”（原文我忘了
很好奇這個轉速是怎麼被測得的？
有請各位大大解惑，謝謝！
順便恭喜Lu拿下寧波挑戰賽男單冠軍！！
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