题干

如图所示,小球从竖直砖墙某位置静止释放,用频闪照相机在同一底片上多次曝光,得到了图中1、2、3、4、5…所示小球运动过程中每次曝光的位置.连续两次曝光的时间间隔均为T,每块砖的厚度为d。根据图中的信息,下列判断错误的是  

A:位置“1”是小球释放的初始位置

B:小球做匀加速直线运动

C:小球下落的加速度为

D:小球在位置“3”的速度为

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答案(点此获取答案解析)

A

同类题5

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    Papa, as a son of a dirt-poor farmer, left school early and went to work in a factory, for education was for the rich then. So, the world became his school. With great interest, he read everything he could lay his hands on, listened to the town elders and learned about the world beyond his tiny hometown. "There's so much to learn," he'd say. "Though we're born stupid, only the stupid remain that way. "He was determined that none of his children would be denied (拒绝) an education.

    Thus, Papa insisted that we learn at least one new thing each day. Though, as children, we thought this was crazy, it would never have occurred to us to deny Papa a request. And dinner time seemed perfect for sharing what we had learned. We would talk about the news of the day; no matter how insignificant, it was never taken lightly. Papa would listen carefully and was ready with some comment, always to the point.

    Then came the moment—the time to share the day's new learning.

    Papa, at the head of the table, would push back his chair and pour a glass of red wine, ready to listen.

    "Felice," he'd say, "tell me what you learned today."

    "I learned that the population of Nepal is ...."

    Silence.

    Papa was thinking about what was said, as if the salvation of the world would depend upon it. "The population of Nepal. Hmm. Well……" he'd say. "Get the map; let's see where Nepal is." And the whole family went on a search for Nepal.

    This same experience was repeated until each family member had a turn. Dinner ended only after we had a clear understanding of at least half a dozen such facts.

    As children, we thought very little about these educational wonders. Our family, however, was growing together, sharing experiences and participating in one another's education. And by looking at us, listening to us, respecting our input, affirming our value, giving us a sense of dignity, Papa was unquestionably our most influential teacher.

    Later during my training as a future teacher I studied with some of the most famous educators. They were imparting what Papa had known all along—the value of continual learning. His technique has served me well all my life. Not a single day has been wasted, though I can never tell when knowing the population of Nepal might prove useful.