问题 多选题

如图所示,在距地面高为h处,以v0的速度水平抛出一个小球,先后经a、b两点落地.若运动中的空气阻力不计,则下列说法中正确的是(  )

A.小球在a点时的动能小于在b点时的动能

B.小球在a点时的重力势能小于在b点时的重力势能

C.小球在a点时的机械能小于在b点时的机械能

D.小球在a点时的机械能等于在b点时的机械能

答案

A、B小球从a到b的过程中,重力做正功,根据动能定理得:动能增大,重力势能减小,故A正确,B错误.

C、D由于不计空气阻力,只有重力做功,小球的机械能守恒.故有小球在a点时的机械能等于在b点时的机械能.故C错误,D正确.

故选AD

阅读理解

Sports can help you keep fit and get in touch with nature. However, whether you are on the mountains, in the waves, or on the grassland, you should be aware that your choice of sport might have great influence on the environment.

Some sports are resource-hungry. Golf, as you may know, eats up not only large areas of countryside, but also tons of water. Besides, all sorts of chemical and huge amounts of energy are used to keep its courses in good condition .This causes major environmental effects. For example, in the dry regions of Portugal and Spain, golf is often held responsible for serious water shortage in some local areas.                                    

There are many environment-friendly sports.Power walking is one of them that you could take up today. You don’t need any special equipment except a good pair of shoes; and you don’t have to worry about resources and your purse. Simple and free, power walking can also keep you fit. If you walk regularly, it will be good for your heart and bones. Experts say that 20 minutes of power walking daily can make you feel less anxious, sleep well and have better weight control.

Whatever sport you take up, you can make it greener by using environment-friendly equipment and buying products made from recycled materials. But the final goal should be “green gyms”. They are better replacements for traditional health clubs and modern sports centers. Members of green gyms play sports outdoors, in the countryside or other open spaces. There is no special requirement for you to start your membership. And best of all, it’s free.

小题1:What do we know about golf from the passage?

A.It is not played in Portugal and Spain at all.

B.It causes water shortages around the world.

C.It pollutes the earth with chemicals and wastes.

D.It needs water and electricity to keep its courses green.小题2:The author uses power walking as an example mainly because ________.

A.it is an outdoor sport

B.it improves our health

C.it uses fewer resources

D.it is recommended by experts小题3:The author writes the passage to ________

A.show us the function of major sports

B.encourage us to go in for green sports

C.discuss the major influence of popular sports

D.introduce different types of environment-friendly sports

多项选择题