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 child, starting from rest at the top of a 3.00-m tall slide, has a speed of 2.52 m/s at the bottom ofthe slide. What percent of the mechanical energy of the child-Earth system at the top of the slideremains when the child reaches the bottom of the slide?
A. 8.4%
B. 10.6%
C. 32.5%
D. 46.0%
E. It cannot be determined without knowing the mass of the child.
参考答案: B
本题详细解析:
$PE_g=KE+T E_friction$; With no friction, child would be traveling at 7.75 m/s at bottom of slide. $P E_g =mgh=30m$;$KE=\frac{1}{2}mv^2=3.18m$;$\frac{3.18m}{30m}(100)=10.6%$
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