跳板跳水运动员，在跳板跳水比赛中，总是尽可能把板压弯一点，然_爱下问搜题

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问题填空题

跳板跳水运动员，在跳板跳水比赛中，总是尽可能把板压弯一点，然后再高高腾起，如图所示．如果不计空气阻力，则运动员在腾起的过程中，重力势能在______（填“增大”、“减小”或“不变”），在下落过程中，动能在______（填“增大”、“减小”或“不变”），在腾起和落下的整个能量转化过程中，运动员的机械能总量______（填“增大”、“减小”或“不变”）．

答案

（1）运动员在腾起的过程中，高度逐渐增大，因此重力势能在增大；

（2）在下落过程中，速度逐渐增大，因此动能也在增大；

（3）由于不计空气阻力，因此在腾起和落下的整个能量转化过程中，运动员的机械能总量不变．

故答案为：增大；增大；不变．

完形填空

Mr. Jackson was on duty that evening. It was 1 and there was thick snow outside. So few people came to the hospital and he could 2 on the bed in his office and soon he went to sleep . Suddenly someone knocked at the door and it woke him up. He got up and opened the door. In went an old man. His wife was ill and he asked the doctor to go to look her over.
　It was still 3 when Mr. Jackson came out. The old farmer walked fast and he hardly catch up with him. It was 4 for him to walk on the snowy roads. When he got to the man’s house, he was very 5 . He looked over the old woman and found she had a bad cold. He gave her some 6 and began to return to the hospital. The wind was blowing strongly and he couldn’t walk too 7 .
　And when he was near the hospital, he had a pain in his foot.
　He walked slowly and at last he went into his office, He took 8 his shoe and looked at his foot. There was much blood on it. He 9 he stepped on a broken glass. He looked at his shoe carefully and said to 10 “Luckily, it didn’t prick my shoe!”

问答题

简述急性心肌梗死胸痛的特点。