题干

竖直升空的模型火箭,其v﹣t图象如图2所示,由图可知(  )

A:火箭经过6s落回地面

B:火箭经过6s到达最高点

C:火箭上升的最大高度为120m

D:火箭上升过程中的加速度大小始终是20m/s2

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答案(点此获取答案解析)

B,C

同类题5

The man had died when the rescuers found her after the terrible earthquake. She was covered by a destroyed house. Through gaps (缝隙) of those ruins,the rescuers could see her last posture (姿势).It was something like an ancient person who was kowtowing (叩头),but it just looked strange because she was out of shape by pressure.

The rescuers confirmed her death by touching her through the gaps of the ruins. They shouted at the ruins again and again,knocked the bricks using various tools,but no reply inside.

Then the rescuing team went to the next building. Suddenly the leader ran back,calling“Come here.” He came to the body,put his hands under the woman,feeling and touching,then shouted loudly and gladly,“There is someone,a baby,still living.”

T hrough some efforts,re scuers cleaned up the ruins which blocked her. Under her body lay her baby,who was covered by a small red quilt(棉被).He was about 3 or 4 months’ old. Since well protected by his mother’s body,he was safe. He was in a deep sleep when the rescuer carried him out,and his lovely and peaceful face warmed everyone around him. The doctor,along with the rescuing team,took the baby out of the quilt to check if the baby was all right,and he found there was a mobile phone in the quilt. The doctor looked at the screen;a written me ssage was already there:“My dear baby,if you could live,don’t forget how much I love you. ”As a doctor,he experienced much of this type of separation;but at this moment,he cri ed. The mobile phone was passed,and every person who saw this message shed (流出)tears.