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]
You drop a rock off a bridge into the river below and hear the splash 2.5 s later. How far above theriver is the bridge?
A. 25 m
B. 27 m
C. 29 m
D. 31 m
E. 33 m
参考答案: C
本题详细解析:
Falling: $x_{fall}=v_0 t +\frac{1}{2}at^2$;
sound: $x_{sound}=(v_{sound})t$
$x_{fall}=x_{sound}$;
$\frac{1}{2}(10 \frac{m}{s^2}) t^2 = 340 \frac{m}{s} (2.5s-t)$
t=0.085s
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