题干

以下是我们生活中常见到的几种现象:

①篮球撞击在篮板上被弹回;

②用力揉面团,面团形状发生变化;

③用力握小球,球变瘪了;

④一阵风把地面上的灰尘吹得漫天飞舞.

在这些现象中,物体因为受力而改变运动状态的是(   )

A:①②

B:①④

C:②③

D:②④

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答案(点此获取答案解析)

B

同类题5

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    We often hear stories of animals rescuing people .But now someone has managed to return the favor .

    The event took place one snowy January morning Thomas Smith was walking his dog, Jack, in the park." As I was walking, I just saw Jack running onto the ice towards the ducks in the middle, and then he fell into the water and couldn't climb out, "said Smith.  He realized he had no choice but to try and save his dog." someone else told me the lake was only one - meter deep, but it was at least twice that. I had to break my way through the 6- cm ice. Finally, I got Jack by the neck, and pulled him out. I don't think I have ever felt so cold by the time we got back to dry land. And when we got there, everyone was asking if Jack was okay------ no one was particularly worried, about me!"

    A neighbor, Julie Brown, saw it all happen."The dog went onto an icy lake. All of a sudden, it started to go under. There were crowds of people around, and they were all shouting and screaming. Before I knew it, the owner Smith was in the water forcing his way through the ice. I can't begin to imagine how cold it was. Everyone was very nervous, but he was as cool as a cucumber — he just crawled back out, put the dog on its lead, and went home."

    Many regard him as a hero, but Mr. Smith is quite laid- back about it."Most dog owners are the same as me.They would do what I did without a second thought. But in the future, I'm going to make sure he's on lead near any ice ponds,

    Pets are members of our family. Would you do the same for them?