问题
选择题
| 关于力对物体做功，以下说法正确的是（ ） |
A．一对作用力和反作用力在相同时间内做的功一定大小相等，正负相反 B．不论怎样的力对物体做功，都可以用W=Fscosα C．合外力对物体不作功，物体必定做匀速直线运动 D．滑动摩擦力和静摩擦力都可以对物体做正功或负功 |
答案
答案：D
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| 关于力对物体做功，以下说法正确的是（ ） |
A．一对作用力和反作用力在相同时间内做的功一定大小相等，正负相反 B．不论怎样的力对物体做功，都可以用W=Fscosα C．合外力对物体不作功，物体必定做匀速直线运动 D．滑动摩擦力和静摩擦力都可以对物体做正功或负功 |
答案：D
As a teacher, my daily activity involves driving to a new school almost every day. On one particular day during my lunch break, I drove to a nearby square to get a coffee. Upon returning to the 36, I realized I had locked my phone and my 37 inside! I had about 15 minutes to get back to the 38. So I hurried into a McDonald’s in the same square, and asked the man at the counter, who happened to be the 39, to call a taxi for me. After I 40 explained my situation to him, he rushed inside to make the phone while I waited anxiously in the restaurant. I had less than 10 minutes to 41 to my school at this point. A moment later, the manager returned only to tell me that the line was 42, and that he had not been able to 43 the taxi yet. I think both 44 and fear could be seen in my face. Without a thought, he grabbed his coat and 45 to drive me to the school. Without hesitation, I followed him into his car and got back to the classroom with two minutes to 46 before the bell rang! This experience made me 47 that out of every seemingly hopeless situation, there is the opportunity for acts of kindness to happen, which has an unimaginable influence on those who receive them.
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