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问题 多选题

在两个物体相互作用过程中，下列说法中正确的是（　　）

A．质量大的物体动量变化大

B．两物体的动量变化大小相等

C．质量大的物体速度变化小

D．两物体所受的冲量相等

答案

D、根据牛顿第三定律得知，作用力与反作用力大小相等、方向相反，而且同时产生，同时消失，作用时间相等，由冲量定义式I=Ft，可知作用力与反作用力的冲量也是大小相等、方向相反．所以两物体所受的冲量不相等．故D错误．

B、C、D根据动量定理得：I=△P，则知，两物体的动量变化量大小相等，方向相反．

又△P=m?△v，则得△v与m成反比，质量大的物体速度变化小．故BC正确，A错误．

故选BC

选择题

下图为一个反射弧模式图，有关分析中，正确的是

①S是感受器，M是效应器　 ②S是效应器，M是感受器 ③Ⅰ是传入神经，Ⅲ是传出神经　

④Ⅰ是传出神经，Ⅲ是传入神经　 ⑤兴奋的传导方向是：SⅡM　

⑥兴奋的传导方向是：MⅡS　 ⑦兴奋的传导方向是：SⅡM或MⅡS

[ ]

A．①③⑤

B．②④⑥

C．①③⑦

D．②④⑦

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单项选择题

Randy Kraus was paralyzed. His left side was useless. But his right hand was (1) enough to lift a bucket to his forehead. Once, he’d been a police officer and owned a private-eye agency. Once, he’d been p and able. Now, he felt he was nothing.
His (2) started with Parkinson’s disease, but it didn’t (3) there. In July 2002, the 60 year old Kraus went into the hospital for an operation to control the shaking. (4) , during the operation, he had a stroke. He was paralyzed. The (5) man, who loved golf, could think, but couldn’t (6) . Kraus wanted the doctors to (7) it to him straight. "You may never walk again, " they told him. "Maybe you won’t (8) be able to talk. "
Once at home, he (9) he couldn’t lift a fork or take a drink by himself. Physical treatment was so painful and slow. What did he have to (10) for So now Kraus held the gun against his head. (11) the cold metal on his skin, he began to consider not his pain, but the pain he (12) cause his wife, daughters and grandchildren. He didn’t pull the trigger.
"You are where you are", his exercise physiologist, Andrew Garud told him. "The pace would be slow; the pain would be (13) . But as long as you are (14) , you have the ability to get better. " After three months of (15) with Garud, Kraus wanted to see if he could (16) . He could. Then he took three steps, sat down and cried like a baby. One step (17) to another. Next he managed a short walk. It was the hardest (18) of Kraus’s life.
Garud kept saying he could (19) more. Now, Kraus can brush his teeth, shave himself and get around the house with a walker. Little success only the paralyzed can (20) understand.

A．fight
B．adventure
C．lesson
D．defense
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