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问题 计算题

质量为M的木块在光滑水平面上以速度v1向右运动，质量为m的子弹以速率v2水平向左射入木块，假设子弹射入木块后均未穿出，且在第N颗子弹射入后，木块恰好停下来，求N的数值。

答案

解：取水平向右为正方向，对木块与N颗子弹组成的系统，由动量守恒定律得：

Mv1－Nmv2＝0

N＝

填空题

用括号中动词的适当形式填空。

     Bob and Jim once worked in the same factory. One day, Bob (1)_________ (lend) Jim one hundred

dollars,but then Jim (2)________ (leave) his job and (3)________ (go) to work in another town without

4)________ (pay) back the money. Bob (5)_________ (not see) Jim for a year, later he found out from

another friend that Jim was in another town and (6)________ (stay) at a hotel,so he went there (7)_________ (meet) him late in the evening. When he got to Jim's room, he saw his shoes near the door."Well, he

(8)________ (be) in," he thought, and knocked at the door, and (9)_________ (say),"I know you are in,

Jim. Your shoes are out here." "I (10) _________(go) out in my boots," answered Jim.

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单项选择题 案例分析题

患者女，27岁，右下后牙牙龈肿痛5天，进行性加重。现开口受限，局部跳痛。检查见近中阻生，冠周红肿，触痛。挤压有脓液从远中袋溢出

肿胀局部处理方法为（）.

A.牙周治疗

B.切开引流

C.拔除

D.开髓，根管引流

E.口服抗生素，局部不做处理
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