本题目来源于试卷: 美国2021年物理杯赛真题 PHYSICS BOWL 2021，类别为 美国物理杯赛(Physics Bowl)
[单选题]
A man of mass m, gets off a boat by leaping to the left in an exactly horizonal direction. Both the manand the boat were initially stationary. Immediately after the leap, the boat of mass M, is observed tobe moving to the right at speed v. What is the increase of the kinetic energy in the man-boat system?(Neglect the resistive force of the water)
A. $\frac{1}{2} Mv^2 $
B. $\frac{1}{2} mv^2$
C. $\frac{1}{2} (M+m)v^2$
D. $\frac{1}{2} (M+\frac{m^2}{m}) v^2$
E. $\frac{1}{2} (\frac{Mm}{M+m}) v^2$
参考答案: D
本题详细解析:
$KE=\frac{1}{2} Mv^2$ $\frac{1}{2} Mv^2 + \frac{1}{2} Mv^2$ $m(\frac{MV}{m}^2)=\frac{1}{2} (m+\frac{M^2}{m}) v^2$
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