如图所示，F1、F2、F3和F4为同一水平面内的四个共点力，它们的大小分别是F1=2N、F2=3N、F3=3
N、F4=4N，它们之间的夹角依次为60°、90°和150°，F1的方向为正东方向．试用正交分解法求它们合力的大小和方向．3
1、建立坐标系如图．
2、根据平行四边形定则将各力垂直分解到两个坐标轴上．
3、分别求出x轴和y轴上的合力，
x轴方向的合力Fx=F1+F2cos60°+F4cos60°-F3cos30°=1N
y轴方向的合力Fy=F2sin60°+F3sin30°-F4sin60°=
N3
所以四个力的合力大小为
F=
=2N，方向东偏北60°．
+F 2x F 2y
答：四个力的合力大小为2N，方向东偏北60°．
如表是客运轮船在上海至九江运行时刻表，请根据表中的数据回答下列问题：
| 上行 | 港名 | 下行 | 距离（千克） |
| 11：：00 | 上海 | 12：30 | 0 |
| 17：00 18：10 | 南通 | 06：00 05：50 | 128 |
| 21：00 21：20 | 江阴 | 03：30 03：20 | 188 |
| 镇江 | 205 | ||
| 07：00 07：30 | 南京 | 19：10 18：40 | 392 |
| 12：30 13：50 | 芜湖 | 14：50 14：20 | 488 |
| 17：40 18：00 | 铜陵 | 10：40 10：10 | 596 |
| 23：40 | 九江 | 05：30 | 856 |
（2）轮船在南通停靠______分钟；
（3）旅客从上海上船到九江准点下船共用______小时______分钟．
| 完形填空。 | ||||
| There was a time when I thought my dad didn't know a thing about being a good father. I couldn't 1 him ever saying the words "I love you." It seems to me his only purpose in life was to say " 2 " to anywhere I wanted to go and anything I wanted to do, including getting a 3 . Some parents bought their kids cars when they got their driver's licenses. Not my dad -he said that I'd have to get a job and buy my own. So that is what I did. I got a job at a very nice restaurant and 4 every penny I could and 5 I had enough to buy my car, I did! The day I brought that car home, my dad was the first one I wanted to 6 to. "Look, dad, a car of my own. If you ever want a ride, I'll only 7 you five dollars." I offered with a smile. "I see," was all he said. One day, there was something wrong with my father's truck. So he needed a 8 to work. The sun wasn't even up when we left the house , 9 it was already getting warm out. It was going to be a(n) 10 day. As I dropped my dad off, I 11 him, dressed in his work clothes, getting his 12 from the truck (车尾箱) of my car. Watching his sun-weathered face, and even from a distance I could tell there were 13 lines than I ever remembered being there before. I realized how hard my dad works for the family. My father is a cement finisher(水泥修整工). At that moment, it 14 to me that he actually got down on his hands and knees to sweat over hot concrete(混凝土) to make a living for his family. And he did this day in and day out, 15 hot it got. Never, not once, had I heard him 16 about it. To him we were "worth" it. And never once did he "charge" us for it. When he closed the trunk, his tools set off to the side, he walked over to my window to 17 me five dollars. I rolled down the window and said "Good-bye, dad. Keep your five dollars. It's my 18_ . Don't work too hard. I love you." His 19 met mine, then glanced away in the direction of his waiting tools, he 20 his throat(喉咙, 嗓子) and said, "Oh, and… | ||||
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