题目

Why do we say “it’s not the winning but taking part that counts”? It’s a phrase supported by the founder of the Olympics, Baron Pierre de Coubertin, who said “The most important thing in the Olympic Games is not winning but taking part: the important thing in life is not conquering but fighting well.” Most people seem to agree that trying and failing is more admirable than not trying at all. In practice, though, most people seem only to be interested in the medals. In young children’s sporting events, last place is often rewarded with a “wooden spoon” or booby prize在光滑的水平面上相距40cm的两个钉子A和B，如图所示，长1m的细绳一端系着质量为0.4kg的小球，另一端固定在钉子A上，开始时，小球和钉子A、B在同一直线上，小球始终以2m/s的速率在水平面上做匀速圆周运动．若细绳能承受的最大拉力是4N，那么，从开始到细绳断开所经历的时间是(  ) A．0.9πs　　　　　　　　　　　　　　　　 B．0.8πs C．1.2πs　　　　　　　　　　　　　　　　 D．1.6πs