问题
不定项选择
下列说法正确的是
A．两分力大小一定，它们的夹角在0°到180°之间时，夹角越大，则合力越小
B．用两根绳子吊起一重物，使重物保持静止(如图)，缓慢地增大两绳之间的夹角θ，则在这过程中两绳对重物拉力的合力将变大
C．压力是由于物体受重力作用而产生的
D．放在桌面上的皮球受到的弹力是由桌子发生形变产生的
答案
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下列说法正确的是
A．两分力大小一定，它们的夹角在0°到180°之间时，夹角越大，则合力越小
B．用两根绳子吊起一重物，使重物保持静止(如图)，缓慢地增大两绳之间的夹角θ，则在这过程中两绳对重物拉力的合力将变大
C．压力是由于物体受重力作用而产生的
D．放在桌面上的皮球受到的弹力是由桌子发生形变产生的
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| Smiling is the best way of making friends. When I was thirteen 1 old, my father found a job in the city. So my family moved there. I also came to a 2 school near where we live. My old school was far away. At first, I did not know anyone in my class. I was very lonely 3 I was afraid to make friends with my classmates. I 4 talk to anyone about my problem, and I didn't want my parents to 5 me. Then one day, something good happened. I was sitting at my desk 6 as usual while my classmates were talking happily with each other. At that moment, 7 came into the classroom. I didn't know who he was. He passed me and then turned back. He looked 8 me and, without a word, smiled. Suddenly, I felt happy, lively and warm. That smile changed my life. I started to talk with the other classmates and made friends. Day by day, I became 9 to everyone in my class. 10 the smile, I have moved on to a new life. Now, I believe that the world is what you think it is. So smile at the world and it will smile back. | ||||
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