题干

小杰同学在游玩“海底世界”时,观察到鱼嘴里吐出的气泡上升时的情况如图所示,对气泡上升时气泡内气体压强分析正确的是(   )

A:压强不变

B:压强变小

C:压强变大

D:无法确定

上一题 下一题 0.0难度 选择题 更新时间:2017-04-15 01:12:54

答案(点此获取答案解析)

B

同类题3

阅读下面的文字,完成下面小题。

材料一:

    研究发现,创新型的智能共享单车在进入城市不到一年时间里,成为小汽车、公交、地铁外的第四种重要交通工具,实现了“自行车王国”的人性化复兴。智能共享单车代表着和谐的生活方式,代表着“互联网+”与实体经济的完美结合。不仅带回了自行车川流不息的生活气息,还促进市民积极参与城市共建,推动了城市文明、低碳、智慧、健康的发展。

    共享单车出现后,小汽车占总出行量的比例由29.8%明显下降至26.6%,而自行车骑行的占比由5.5%翻了一倍至11.6%。共享单车还对节能减排做出了卓越贡献。以智能共享单车摩拜平台为例,在不到一年的时间里,骑行总距离超过25亿公里,减少碳排放量54万吨,相当于多种了3000万棵树。此外,共享单车在提高出行效率,缓解城市拥堵方面也具有明显优势。以北京为例,当出行距离小于5km时,92.9%的情况下,共享单车+公共交通出行比小汽车更快。

    共享单车的兴起不仅可以缓解道路拥堵,对节省城市空间,更有效地利用城市空间也多有助益。以北京为例,一辆小轿车的停车位可供约10辆共享单车停放,如有更多人选择以骑行替代开车,则共享单车可为北京节省约5个鸟巢面积的城市空间。

(摘编自《2017共享单车与城市发展白皮书》)

材料二:

    从用户的出行场景来看,高达62.9%的用户使用共享单车完成地铁站/车站和目的地之间的距离。共享单车目前主要投放的地点是人口稠密的大城市,车站/地铁站和目的地之间容易形成短途出行的高频需求。49.5%的用户会在步行过程中看到单车就使用以节省出行时间,这说明随机偶遇式的用车出行场景非常多,单车提高了人们的出行效率。可见用户使用共享单车的出行率与目的地之间的距离紧密相关。“企鹅智酷”对共享单车用户的单次骑行距离的调研情况如下图:

材料三:

    近日,全球智能共享单车行业首创者和领导者摩拜单车宣布新一轮融资超过6亿美金,为摩拜海外扩张的国际化路途提供了雄厚的资金支撑,争取2017年覆盖全球200个城市,摩拜的扩张速度已经成为全球成长最快的创业企业。摩拜的发展更是如虎添翼,首先在技术层面,物联网实景化和人工智能领域将有更加深入的研发,在未来,消费者会感受到全新的高科技共享单车,让骑行之旅变得更加快速、便捷、开心。科技上的实力让摩拜实现了全面领跑行业发展。

(摘编自2017年06月19日《消费日报》)

同类题5

阅读理解

    You may have heard of the American Dream, an ideal that has powered the hopes of Americans for generations.

    It began as a belief that the US was a land of opportunity, and that anyone could achieve success through hard work. At times, the dream has referred to home ownership, a good job, retirement security or each generation doing better than the last.

    Yet today, this concept seems to have greatly changed. As Time magazine pointed out, quite different from the older generation, many Millennials (the generation born after 1980) redefine(重新定义) the American Dream as “day-to-day control of your life”. They “prize job mobility, flexible schedules, any work that is more interesting than typing, and the ability to travel”, said the magazine.

    Home ownership, once the cornerstone of the American Dream, is becoming a smaller priority for this generation. Meanwhile, nearly 40% of them choose travel as part of their dream. And entrepreneurship(创业) is a rising favorite, as nearly 26% of Millennials consider self-employment as part of their dream.

    So what has led to this huge change?

    Many point fingers at the poor economy. “Modern young Americans seem bound to face a world stamped by ever narrowing opportunity and social stagnation(停滞),”noted The Daily Beast.

    “The rate of 16-to 24-year-olds out of school and out of work is unusually high at 15%. Many college graduates have taken jobs that don't require a degree,” Time reported.

    The magazine worries that these difficulties may lead to a lost generation who are “unable to ever truly find their feet on the corporation's ladder”.

    Dan Kadlec, a reporter of Time, sees Millennials as resetting their expectations.”This situation is different for young adults today,” he wrote. “A true American dream has to feel attainable, and many Millennias are feeling they can only attain a day-today lifestyle that suits them.”