下列各个过程中，属于动能转化为势能的是（ ）
A．张紧的弓把箭射出去
B．钟表里的发条带动齿轮转动
C．向上抛出的石块在空中上升
D．一儿童从滑梯的顶端滑到底端
A、张紧的弓把箭射出去，弹性势能转化为动能，不符合题意；
B、钟表里的发条带动齿轮转动，弹性势能转化为动能，不符合题意；
C、向上抛出的石块在空中上升，动能转化为重力势能，故符合题意；
D、一儿童从滑梯的顶端滑到底端，重力势能转化为动能，不符合题意．
故选C．
| 补全对话,其中有两项为多余选项. | |
| A: Excuse me,sir. Where is the post office? B: 1 may ask the policeman over there. A: Thank you all the same. (The man goes to the policeman.) A: Excuse me. 2 C: Oh,there isn't a post office near here,but there is one near the supermarket. A: 3 C: It's about two kilometers (千米) away. A: 4 C: You'd better take a taxi. Because it's so late,there aren't any buses now. A: 5 C: You're welcome. | |
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