问题 选择题

为了让乘客乘更为舒适,某探究小组设计了一种新的交通工具,乘客的座椅能随着坡度的变化而自动调整,使座椅始终保持水平,如图所示,当此车匀速上坡时,下列说法正确的是(  )

A.乘客处于超重状态

B.乘客所受合力大小越来越小

C.乘客所受的合力方向沿斜面向上

D.乘客所受合力为零

答案

对乘客受力分析,受重力、支持力、可能有静摩擦力,设向前,为f,由于乘客随车做匀速直线运动,故受力平衡,根据共点力平衡条件可以判断,静摩擦力为零,支持力等于重力;

故选D.

单项选择题
阅读理解

People believe that climbing can do good to health. Where can you learn the skill of climbing then? If you think that you have to go to the mountains to learn how to climb, you’re wrong. Many Americans are learning to climb in city gyms(体育馆). Here, people are learning on climbing. The climbing wall goes straight up and small holding places for hands and feet.

How do people climb the wall? To climb, you need special shoes and (保护带) around your chest to hold you. There are ropes(绳索)tied to your. The ropes hold you in place so that you don’t fall. A beginner’s wall is usually about 15 feet high, and you climb straight up. There are small pieces of metal that stick out for you to stand on and hold on to. Sometimes it’s easy to see the new piece of metal. Sometimes, it’s not. The most difficult is your fear. It’s normal for humans to be afraid of falling, so it’s difficult not to feel fear. But when you move away from the wall, and the ropes hold you, and you begin to feel safe. You move slowly until you reach the top.

Climbing attracts people because it’s good exercise for almost everyone. You use your whole body, especially your arms and legs. This sport gives your body a complete workout. When you climb, both your mind and your body can become stronger.

小题1:What can we infer from the passage?

A.People are fairly interested in climbing nowadays.

B.It is impossible to build up one’s body by climbing.

C.People can only learn the skill of climbing outdoors.

D.It is always easy to see holding places in climbing.小题2:The most difficult thing to do in wall climbing is _______.

A.to tie ropes to your

B.to control your fear

C.to move away from the wall

D.to climb straight up小题3:The word “workout” underlined in the last paragraph most probably means _________.

A.settlement

B.exercise

C.excitement

D.tiredness小题4:Why does the author write this passage?

A.To tell people where to find gyms.

B.To prove the basic need for climbing

C.To encourage people to climb mountains.

D.introduce the sport of wall climbing