题干

某工地上,一架起重机将放在地面的一个箱子吊起.箱子在起重机钢绳的作用下由静止开始竖直向上运动,运动过程中箱子的机械能E与其位移x关系的图象如图所示,其中O~x1过程的图线为曲线,x1~x2过程的图线为直线.根据图象可知(   )

A:O~x1过程中钢绳的拉力逐渐增大

B:O~x1过程中箱子的动能一直增加

C:x1~x2过程中钢绳的拉力一直不变

D:x1~x2过程中起重机的输出功率一直增大

上一题 下一题 0.0难度 选择题 更新时间:2013-07-22 03:10:38

答案(点此获取答案解析)

C

同类题4

阅读下列短文,从每题所给的A、B、C和D四个选项中,选出最佳选项,并在答题卡上将该项涂黑。(每小题2分)

A

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