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问题 填空题

如图所示，物体静止在光滑水平面上，现用沿水平面的力F作用于物体上的O点，若要使物体受到沿O指向O′方向的合力，必须同时再加一个力，这个力的最小值是__________，方向为__________。(已知F与OO′都在同一水平面内，F与OO′间的夹角为θ)

答案

Fsinθ，垂直于OO′向上

阅读理解

阅读理解。

     Look at this boy. He is an English boy. His first name is Alan. His last name is Brown.This is his school. His school ID card is 36872368. His teacher is Miss Black. She is a nice teacher. Look! What’s that? It’s backpack. It’s blue. It’s Alan’s backpack. His red jacket is in it. Where is his watch? Oh, Alan lost it this morning.

1. Alan’s family name is ______________.

2. Alan’s school ID card number is ______________.

3. The color of his backpack is _____________.

4. The color of his jacket is ______________.

5. Alan lost ______________ this morning.
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问答题

列举我们身边造成水污染的两种行为，同时对防治水污染提出两条措施．
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