如图是四冲程汽油机的 冲程，某台四冲程汽油机工作时，飞轮的速度是1200r/min，该四冲程汽油机每秒对外做功 次。
做功；10.
题目分析：观察插图可知，进气门和排气门均关闭，活塞向下运动，由此可知此冲程为汽油机的做功冲程；
汽油机的一个工作循环中包括四个冲程，活塞来回两次，曲轴转动两周，对外做一次功；由题意可知，该汽油机飞轮的转速为1200r/min，因此每秒内飞轮转动
，每两转对外做一次功，因此该汽油机每秒内对外做功10次。
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| It has been difficult to sit on the bench the majority of my high school basketball career,to watch my team from the sideline and 1 why I am not good enough to be on the floor. 2 endless hours of work and devotion, pushing myself through drill after drill, the 3 thing I want is to be a cheerleader. The feeling of being 4 is sometimes too much and drives me to 5 on the spot. I often feel as though my efforts are wasted and my time is eaten away, devoted to 6 . It is heartbreaking to be a spectator(旁观者) for the game I love,knowing that no one has enough 7 to give me the chance to 8 on the floor. Tears well up, but I hold them back. I shouldn't be so 9 over something so silly. Away from the game, it's easier to put my thoughts together, 10 letting my emotions drive my reasoning. I consider 11 I am where I am. I have played football my whole life. I have a passion for the 12 and always have. There is nothing like the excitement of 13 : the swish of the net, the sweat rolling off my cheeks, even the bruises(青肿) are battle wounds worn 14 after every game. Even if I don't play much, I participate in every 15 . I am part of a team of girls who 16 together like a family. I am there for them, 17 they are for me. Should I move on? Or should I stay with my team and pursue my passion just a little longer? The decision isn't difficult when I consider the 18 that being a part of a team brings me -and not just any team, 19 my team. I love basketball and my teammates. When I think about that, my view from the bench really isn't so bad 20 . | ||||
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