题干

一辆汽车在刹车过程中,其运动位移与时间关系为x=8t﹣2t2则(   )

A:这辆汽车在刹车过程用时为4秒

B:这辆汽车的初速度为8m/s

C:这辆汽车在前3s内的路程为8m

D:这辆汽车刹车的加速度为4m/s2

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答案(点此获取答案解析)

B,C

同类题3

阅读材料,完成下列要求。

    中国女药学家屠呦呦获得2015年诺贝尔生理学或医学奖,是首位获得诺贝尔科学奖项的中国女科学家。

材料一上世纪六七十年代,在极为艰苦的科研条件下,屠呦呦团队与中国其他机构合作,研制380多个样品,并从《肘后备急方》等中医药古典文献中获取灵感。因屠呦呦既有中医学知识,也了解药理学和化学,她将东西方医学相结合,达到了一加一大于二的效果。屠呦呦的发明是这种结合的完美体现,先驱性地发现了青蒿素,开创了疟疾治疗新方法,是第一个证实青蒿素可以在动物体和人体内有效抵抗疟疾的科学家。

材料二疟疾是危害严重的世界性流行病,全球百余国家年约三亿多人感染疟疾。在国内外大量工作未获成功的情况下,领导科研组以现代科学继承发扬祖国医药学遗产为指导思想,收集二千多种药方基础上,归纳编纂成《抗疟方药集》,又从中选200多方药,组织筛选。特别结合古代用药经验,从东晋葛洪《肘后备急方》青蒿“绞汁”服用截疟记载中,考虑到温度、酶解等因素,创新引入西医炼药技法,不断改进提取方法,终于在1971年获得青蒿抗疟发掘成功,使全球数亿人因这种“中国神药”而受益,被认为是近五十年来人类治疟的最大进步,并将随着其推广显示出更大的效益。

同类题5

阅读理解。

    I arrived at my mother's home for our Saturday family dinner. The smells of food flew over from the kitchen. Mother was pulling out quilt after quilt from the boxes, proudly showing me their beauties. I knew they were all made herself. She was preparing for a quilt show on TV. When we began to fold and put them back into the boxes, I noticed something at the bottom of one box. I pulled it out. “What's this?” I asked.

“Oh?” Mom said, “That's Mama's quilt.”

    I spread the quilt. It looked as if a group of school children had made the pieces together.

 “Grandmother made this?” I asked in surprise. My grandmother was a master at making quilts. This certainly didn't look like any of the quilts she had made.

  “Yes, right before she died. I brought it home with me last year and made some changes,” Mom said, “I'm still working on it. See, this is what I've done so far.”

     I looked at it more closely. She had made a line straight(直的). At the center of the quilt, she had stitched a piece of cloth with these words:    “My mother made many quilts. She didn't get all lines straight. But I think this is beautiful. I want to see it finished. Her last quilt.”

“Oh, this is so nice, Mom.” I said. I was sure now that by completing my grandmother's quilt, my mother was honoring her own mother. I realized that I held in my hands a family treasure. It started with the loving hands of one woman, and continued with the loving hands of another.