the coefficient of restitution
日本野球機構（NPB）は、公式戦で使用している統一球の仕様を変更していたことを明らかにしました。いわゆる「飛ぶボール」のうさわを日本野球機構は否定するという嘘をついていたわけで、またまた野球ファンをないがしろにしていたことになります。
「飛ぶボール」はもちろんflying ballではありませんね。Kyodo電は「よりホームランが出る」という形でおさめています。
Baseball: NPB admits changing ball for this season
TOKYO (Kyodo) -- Nippon Professional Baseball admitted Tuesday it had changed its official ball prior to the start of this season, which has seen markedly more home runs.
The admission comes after 512 home runs were hit in 341 games this season (1.50 per game), an increase of roughly 40 percent over the 1.05 per game hit in the previous two seasons when a new type of official balls was introduced to reduce home runs. NPB originally denied that this season's ball was any different.
Kunio Shimoda, NPB's secretary general, said the move was taken to make the ball conform to the rules, which use a figure known as the coefficient of restitution to measure a ball's liveliness.
"The change was made to bring the coefficient of restitution within the allowable range," said Shimoda, who said it became clear that balls in use through last season did not meet the standards in that respect.
The revelation came about when the players union demanded at an informal negotiation in Sendai on Tuesday to seek test data for the balls and an explanation.
Just two weeks into the season, the increase in home runs sparked questions to NPB, which said on April 15, "The uniform ball's specifications have not been changed." At that time, the ball's manufacturer Mizuno Corp. said the increase in home runs was primarily at domed stadiums and due to foreign batters hitting so many home runs.
http://mainichi.jp/english/english/newsselect/news/20130612p2g00m0sp020000c.html
「飛ぶボール」の訳も気になりますが、併せておさえたいのがthe coefficient of restitution「反発係数」です。物理好きの息子の領域になりますが、これは以下のように説明されています。カット＆コピーです。（UG）
反発検査は日本車両検査協会・東京検査場で行われる。反発係数とは、例えば、時速１００キロで鉄板にぶつかり、時速５０キロではね返れば「０・５」となる。ピッチングマシンから放出される球を約１・５メートル離れた鉄の壁に当て、当たる前の速度とはね返った後の速度で測定。ＮＰＢ公式サイトによると、時速２７０キロ（ボールとバットの標準的な相対速度）で反発係数「０・４１〜０・４４」の範囲に入ると合格とし、厳密な数値を「０・４１３４〜０・４３７４」と定めている。
http://hochi.yomiuri.co.jp/baseball/npb/news/20130611-OHT1T00159.htm
