问题 选择题

在下列情况下,机械能发生了变化的是(  )

A.物体从光滑的斜面上自由滑下的过程

B.跳伞运动员从空中匀速下落

C.汽车在水平公路上匀速前进

D.高空中沿水平轨道匀速飞行的飞机

答案

A、物体从光滑斜面上自由滑下时,重力势能转化为动能,没有摩擦生热现象,机械能守恒,机械能大小不变,A不符合题意;

B、跳伞运动员匀速降落时,其质量不变速度不变,动能不变,但所处高度降低,重力势能减小,所以其机械能减小,B符合题意;

C、汽车在水平公路上匀速前进,其质量、速度、所处高度都不变,动能和重力势能不变,所以其机械能不变,C不符合题意;

D、高空中沿水平轨道匀速飞行的飞机,其质量、速度、所处高度都不变,动能和重力势能不变,所以其机械能不变,D不符合题意.

故选B.

阅读理解

There are some famous buildings that everyone can recognize. When you see a picture of a sports stadium that reminds you of a bird’s nest, you probably know it is the Olympic stadium in Beijing. When you see a picture of a famous concert hall that reminds you of a sailing ship, you probably know it is the Sydney Opera House in Australia. Buildings like these are easily recognized everywhere in the world. They were designed to look like other things if people use their imaginations.

Other buildings do not need any imagination. They are made to look exactly like other things. Sometimes, these buildings are offices, restaurants, or even houses. Three buildings built in this way are actually museums. The shape of the building is clue to the objects people can see inside.

In Guizhou, China, people can visit the Meitan Tea Museum, built in the shape of a giant teapot. There is also a second building next door that is shaped like a huge tea cup. From far away, the nine-story teapot-shaped museum looks like some kinds of giant work of art. But as one gets closer, the windows make it clear that this is a building.

People who are interested in guitars might want to visit the Guitar Museum in Tennessee, USA. The three-story building is shaped like a guitar lying on its side. Inside, visitors can see all kinds of guitars as well as learn about famous guitar players. 

One of the newest funny shaped museums is a pottery museum in Gyconggi, Korean museum, built in 2011, is shaped just like a traditional Korean pot, Along with seeing exam pots and tools used for making pots in the museum, visitors can try to make their own pots.

小题1:Sydney Opera House look like_______and it is in Australia.

A. a bird’s nest    B. a sailing ship    C. a nice guitar

小题2:People can visit the building in the shape of teapot__________.

A. in Guizhou, China   B. In Tennessee, USA   C. in Gycouggi, Korea

小题3:The underlined word” giant” means “_________” in Chinese.

A.豪华的     B. 巨大的     C. 古老的

小题4: Which is NOT true about the building that is shaped like a guitar?

A. People can see all kinds of guitars inside of it.

B. You can find information about famous guitar players there.

C. The two-story building is shaped like a guitar lying on its side.

小题5:The Olympic stadium and the Sydney Opera House are examples of ________.

A. buildings that look exactly like things in them

B. buildings that look like other things

C. buildings that look like famous things

单项选择题