问题 选择题

如图,卷扬机的绳索通过定滑轮用力F拉位于粗糙面上的木箱,使之沿斜面加速向上移动。在移动过程中,下列说法正确的是(     ) 

A.F对木箱做的功等于木箱增加的机械能与木箱克服摩擦力做的功之和

B.F对木箱做的功等于木箱克服摩擦力和克服重力所做的功之和

C.木箱克服重力所做的功等于木箱增加的重力势能

D.F对木箱做的功等于木箱增加的动能与木箱克服摩擦力所做的功之和

答案

AC

题目分析:据题意,由于木箱在拉力作用下做匀加速上升,对木箱受力分析,木箱受到重力、支持力、拉力和摩擦力,据动能定理有:,整理得,则A选项正确而B、D选项错误;由于重力做功与重力势能变化相对,则C选项正确。

问答题 简答题
阅读理解

A couple had a son eleven years after they married. They were a loving couple and the boy was the apple of their eye. When the boy was around four years old, one day the father was very tired after work so he asked his wife to pick up their son. The mother, who was very busy in the kitchen, totally forgot about it.

Later the boy lost his way on the street. When the son was found missing, the mother hurried to look for him, but she didn’t find him. The mother felt very sad and didn’t know how to face her husband.

When the father went to the police station after hearing that the son was missing, he looked at his wife and said just four words. What do you think the four words were? The husband just said "I love you, darling."

The son was missing. If she had picked him up earlier, this would not have happened. There is no point in blaming (责备) anyone. His wife had also lost her only child. What his wife needed at that moment was comfort and understanding from her husband. That is what the husband gave his wife. Several weeks later, with the help of the police, the couple finally found their lost son. The family’s relationship became stronger over that time.

Sometimes we spend lots of time asking who is to blame. We miss many chances to give each other support and let each other feel the warmth of human relationships. Get rid of all your unwillingness to forgive, selfishness, and fears and you will find the world is much more wonderful.

小题1:What is the meaning of the underlined phrase “the apple of their eye”

A.A person who always has a sweet smile in their opinion.

B.A person who is as pretty as an apple in their opinion.

C.A person who is loved more than anyone else in their opinion.

D.A person who looks like an apple in their opinion.小题2:Why didn’t the father pick the boy up himself?

A.He was very lazy.

B.He thought the mother had picked him up.

C.He forgot to pick him up.

D.He was too tired to do it.小题3:What can we learn from this passage?

A.Be careful in everything you do.

B.Love is the most important thing.

C.Learn to forgive others.

D.Everyone can make mistakes.小题4:What do you think of the husband?

A.Warm-hearted.

B.Careful.

C.Hard-working.

D.Broad-minded.