题干

利用废旧牙膏皮可以做很多小实验.如把空的牙膏皮剪去尾部做成一个筒状,放入盛有水的烧杯中发现牙膏皮漂浮在水面上;然后再将此牙膏皮卷成小团状后放入水中,牙膏皮沉入水底.比较前后两种情况,下列说法中正确的是(   )

A:牙膏皮漂浮时受到的浮力比它沉底时受到的浮力大

B:牙膏皮漂浮时受到的重力大于它沉底时受到的重力

C:牙膏皮漂浮时受到的浮力等于它的重力

D:牙膏皮沉底时水对烧杯底的压强比它漂浮时水对烧杯底的压强小

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答案(点此获取答案解析)

A,C,D

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    He was struggling (费劲) to tie his shoes. I was struggling with whether I should help him. I did, and he was thankful.

   “Thank you”, he said.

  “I'm glad I could help. I just thought it would be easier for me to reach.” I said.

    He was a disabled man, and had to look down most of the time. His arms and legs were twisted (扭曲的) terribly, and he couldn't do what the rest of us would consider easy tasks. He always managed to look up to see how you respond to his words, however. He had a big smile, making me feel comfortable.

    I was still on my knees by his wheelchair.

   “Nice shoes,” he said.

  “Thanks. No one ever complimented me on them before,” I said.

  “No one has the same view of the world as I do,” he replied.

  “Tell me about the world as you see it,” I said smiling.

  “Most people can see if someone is comfortable with them or not in their eyes. I see it in their feet,” he said. “If people keep moving their feet, I just let them go, because I know they're not patient with me. I don't want to make people uncomfortable.”

   “What about me?” I asked.

   “I could see your compassion (同情). And then you came down to my level. I was the one who was nervous,” he said. “I don’t normally have someone look me in the eye.”

   “They don't know what they are missing,” I told him.

   “My cold is nothing to brag about (自夸),” he said.

   “But that smile is so big.”

     Yes, and it's not only a big smile but an attitude.