题干

下面,让我们来研究用器械捕捉老鼠的三种方法.

①如图a所示,在地面上放一个较重的罩,它的一端(如图a中的B点)用一根小棍支撑离地,小棍与细线相连,线的另一端拴着食物.当鼠入内吃食时,扯动细线,B端落地,将鼠封在罩内.

②图b画的是另一种捕鼠笼,笼门D被直杆AB拉起时拉弹簧E,用细杆CF上端的球C扣住杆的A端,当鼠入内吃F上的食物时,拉动杆CF,使环C释放A,门D在弹簧E的作用下关闭,将鼠囚禁在笼内.

③图c画的也是一个捕鼠装置,在深缸P的边沿上放一块长木板AB,AB的中点在缸沿上,当老鼠爬上木板去A端吃食时,木板失去平衡而使鼠掉入缸内.

根据以上介绍,请回答下列问题:上述3种捕鼠方法中,主要利用弹性势能捕鼠装置是____;主要利用重力势能捕鼠装置是____.(填序号)

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答案(点此获取答案解析)

b,a

同类题2

阅读下面材料,在空白处填入适当的内容(1个单词)或括号内单词的正确形式。

        While thousands of college students headed for warm climate to enjoy sun and fun during their week off from classes, seven local students had other plans.

        The Northern Essex Community College(NECC) students and one of their teachers spent part of their spring break in New York City, helping repair an area ____ (destroy) by the hurricane.

        “I wanted to see for myself what happened,” said Terry. “I couldn't imagine____it is like to lose your home and everything that you know and the____ (power) effect the hurricane had on thosepeople. I wanted to do something, to understand their feeling of helplessness.”

        The group headed into Brooklyn's RedHook district, which was hit hard by the hurricane. There they met people fromother parts of the country, ____had also volunteered to help. Together, thosevolunteers and the NECC students____ (work) to clear rubbish out of at hree-story building. They put on protective suits and gloves____they enteredthe building.

        Inside the building, the students saw nothing but broken walls and doors and pieces of the building   ____ (lie) all over the place.

The students returned to school with____sense of achievement, a feeling that____helped people in need. I was remarkable how a community lost so much and was still able to recover, and this left the deepest impression____thestudents.