题干

皮球落地后又弹起的闪光照片如图所示.仔细观察该图,你发现了什么现象?这一现象说明了什么?


上一题 下一题 0.0难度 选择题 更新时间:2019-12-06 11:52:36

答案(点此获取答案解析)

答:看到小球被弹起的高度越来越小,原因是小球和空气之间存在摩擦力,机械能转化为内能,机械能不断减小,内能不断增加;

说明:机械能在不断减小.

同类题3

阅读下面短文,掌握大意,然后从各题所给的四个选项(A、B、C和D)中,选出最佳答案。

We live a life surrounded by robots. Nearly every robot has been made in some way1 up to a certain level or temperature. The machine will wait for “feedback” about the water2or temperature before it begins the washing cycle. In this way, a washing machine has been patterned after humans. We depend on  3from our five senses to find out what is happening around us and then make decisions about our actions.

Of course, some machines perform functions like humans, but much 4 than we do, such as calculators. A pocket calculator works faster than a human, never makes mistakes, and doesn’t get  5or bored.

Other robots are very similar to humans in their ability6 new things. In factories, robots can learn to do many different tasks, as they are shown by a human operator. For example, in a car factory, a person will guide a robot’s “arm” and “  7” through the steps of the new job. The robot’s electronic “brain” will   8the information away, memorizing the steps so the next time it9can repeat the   movements without a human operator. When the robot must be moved to a new job, its memory is 10so it is ready to learn the next job. Of course, at any time if there is anything  11in the process, different from the original task, the robot cannot 12 with it. It will signal for an engineer to come for repairs.

Some robots are considered very intelligent because they have more human abilities than others, such as “seeing” 13 cameras for eyes or “feeling” with metal fingers that can14shapes and even temperatures. However, no machine has   15been able to copy the complexity of the simplest, most common person.