本题目来源于试卷: gc physics textbook chapter 3 problems，类别为 IB数学
[问答题]
If you stand motionless under an umbrel qpz2 odx.c/2fnjyp; 7la in a ra4 knmd sicmnwiv80b h,4-l u,r/bgu- 3instorm where the drops fall vertically, you remain relatively dry. However, if you start running, the rain bendrkvmm3ubugn -44, h,c 0i-w/s8li bgins to hit your legs even if they remain under the umbrella. Why?
参考答案: When you stand still under the umbrella in a vertical rain, you are in a cylinder-shaped volume in which there is no rain. The rain has no horizontal component of velocity, and so the rain cannot move from outside that cylinder into it. You stay dry. But as you run, you have a forward horizontal velocity relative to the rain, and so the rain has a backwards horizontal velocity relative to you. It is the same as if you were standing still under the umbrella but the rain had some horizontal component of velocity towards you. The perfectly vertical umbrella would not completely shield you.
本题详细解析:
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