本题目来源于试卷: Physics Unit7: Linear Momentum，类别为 通用国际物理
[单选题]
A railroad car, of mass 20xzyw+. r5ts,u0 kg, rolls with negligible friction on a horengf2rhl42c7t7 i ug7 izontal track with a speed of 10 m/s. A 70-kg stunt man drops straight down a distance of 4.0 m, and lands in the car. How fast will the car be moving af fc lu2eh7 72ng4g7tirter this happens?
A. 2.8 m/s
B. 4.7 m/s
C. 7.4 m/s
D. 10 m/s
参考答案: C
本题详细解析:
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