题干

如图甲所示为市民在公园锻炼上肢力量的画面.该器材相当于一根杠杆(杠杆自重不计),乙图为其简化图,锻炼时手在B点用力向上举手柄将A点的配重抬高,达到锻炼上肢的目的.请在乙图中画出动力臂L1、阻力F2及力臂L2

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解:如图所示:

同类题5

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       A few days ago, I ran into(撞上)a stranger as he passed by. I said sorry to him, and he said, "Excuse me too, I wasn't even watching for you.” We were very polite, this stranger and I.  Then we went on our way after saying goodbye.

       Later in the kitchen at home, as I cooked our meal, my daughter Betty walked up to me, very quietly. When I turned around (转身), I nearly knocked her down  "Get out of the way!" I shouted angrily. She ran away, crying.

       That night, when I lay in bed, my husband said to me, “You were so rude to Betty. Go and look around on the kitchen floor, and you'll find some flowers there. Betty brought those for you. She picked them herself-pink, yellow, and your favourite blue.’’

       When I heard this, I thought deeply: While meeting with a stranger, I was calm and polite; but with my daughter, I was not patient.  I felt sad and tears began to fall.

       I quietly went to Betty's bed, "Wake up, my dear," I said. "Are these the flowers you picked for me?" She smiled, “I found them by the tree. I knew you'd like them, especially the blue.” I said, ‘‘I am so sorry that I treated (对待) you that way today." And she whispered(悄声地说), “Mommy, that's okay- I still love you anyway.’’ I kissed her and said, “I love you too and I do love the flowers.”

       That day Betty gave me a lesson on how to get along with each other in the family. I spent much time on work before and didn't realize how important family life was. I decided to do better in the future.