如图所示，站在树枝上的小鸟受到向上的力的作用，这个力的施力物体是______，同时小鸟将树枝压弯，说明树枝也是______物体．
小鸟站在树枝上，受到两个力的作用：竖直向下的重力；树枝对小鸟竖直向上的支持力．
树枝在对小鸟施加向上的力的同时，其本身变弯，说明小鸟对树枝也有一个竖直向下的力，由此说明树枝也是受力物体．这种现象体现了力的作用是相互的．
故答案为：树枝；受力．
| 完形填空。 |
| Today is October l . It's grandma's birthday. So I go 2 to buy a 3 present for 4 . In a shop, I see a nice scarf. I know my 5 is afraid of cold weather. I want to buy it. It's 6 . I think she will like the green one. I ask the shop assistant to put it in a 7 . The box looks so nice. I take it 8 my grandma. When she 9 it she says happily, " 10 beautiful the scarf is!" |
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