题干

国庆期间人们燃放烟花爆竹进行庆祝,某颗烟花由地面竖直上升20m后,又竖直下落了1m爆炸,则此烟花从地面到爆炸通过的路程和位移的大小分别是 ( )

A:19m、19m

B:21m、19m

C:21m、1m

D:20m、19m

上一题 下一题 0.0难度 选择题 更新时间:2019-03-20 08:58:42

答案(点此获取答案解析)

B

同类题1

阅读理解

    For those who are tired doing the laundry, Samsung has found an answer: a washing machine that can tell you when your laundry is done via a smartphone app(application).

    Strange though it may seem — “my wife already does that” was a common response among attendees viewing the device when it was introduced at the Consumer Electronics Show (CES) this week — Samsung is just one of many appliance makers racing to install (安装) a large number of internet-connected features in machines in an effort to make them “smart”.

    Last year, it was a refrigerator that tweeted. This year, it's Wi-Fi-enabled laundry machines and fridges that can tell you when your groceries are going bad.

    The washers and dryers, available starting in the spring, connect to any smartphone through a downloadable application. The phone can then be used as a remote control, so the machines can be turned on and off while their owners are at work or on the bus.

    Samsung says it's not just something new — the app connection actually has some practical uses.

     “If you started to dry clothes in the morning and forgot to take them out, you can go to your phone and restart your dryer for the time when come home, so your clothes are refreshed and ready to go,” said spokesperson Amy Schmidt.

    The company also says that with electricity rate(电价)varying depending on the time of day, more control over when the machines are used can help save money.

    Perhaps, but what they will probably really accomplish is what all good technologies do —enable laziness. Rather than getting up to check on whether the laundry is done, users will instead monitor it on their phones while watching TV.

同类题5

阅读《笑,不苦口的良药》一文,完成小题。

    ①医学研究证明,笑具有激活人体某些基因的功能。人们通常认为,基因是恒定不变的。但事实上很多基因常常处于休眠状态,或者没有积极地制造蛋白质,通过某种形式的刺激,可以把它们唤醒,笑就是其中一种刺激。

    ②斯坦福大学研究人员曾经对心脏病患者做了一次测试。研究人员首先找来20名心脏病患者,观看半小时分别取自喜剧和悲剧的两部影片片段,两次观看的间隔时间在 8 个小时。然后,通过超声波测量患者肱动脉的血液流速,结果 20 人中有14人在看过令人痛苦的电影片段后,血流速度放缓,但在观看电影中的搞笑片段后,有 19 人血流加速。最后,对患者进行的心电图测试表明,患者观看悲剧电影时对心脏血流速度产生的影响,类似于做心算的影响;而观看喜剧电影相当于进行了一次有氧运动。

    ③人生来就会笑,但很少有人知道,人持续大笑100次,对心脏的血液循环和肺功能的锻炼,相当于划 10 分钟船的运动效果。只要发笑,嘴角和颧骨部位的肌肉便跟着运动,将嘴和两眼向上提拉,这种面部按摩,可以阻止面部线条下坠。每笑一声,从面部到腹部大约有80块肌肉参与运动,不仅具有减少皱纹的功效,还是一种有效的减肥方式。笑,不正是一种保持青春的美容操吗?

    ④不仅如此,笑还是一种最为简单而有效的健身运动。开怀大笑时,随着呼吸肌群的运动,使胸腔和支气管先后扩张,增强了换气量和血氧饱和度,有助于心脏供氧。笑作为一种有效的深呼吸运动,已被越来越多的人们所认识。大笑伴随着腹部肌群的起伏,又是一种极好的腹肌运动,腹肌在大笑中强烈地收缩和震荡,不仅有助于把血液挤入胸腔静脉,改善心肌供血,对胃、肠、肝、脾、胰等脏器也是一种极好的按摩。一张一弛之间,使劳累的肌肉在运动中得以放松。

    ⑤生活需要笑声,的确,每一个人都需要放缓脚步,静观周围美好的事物,凝神谛听大自然的天籁,让绷紧的脸庞舒缓,皱紧的眉宇打开,让微笑在脸上绽放,才能融解人们彼此之间的冰霜和风寒。引人发笑或是接受别人开的玩笑,这意味着你掌握了社会密码,它可以帮助你解决争端,使别人接受你的想法,从而更好地融入集体。通过微笑促进人类心理健康,在人与人之间传递愉悦与友善,增进社会和谐。

    ⑥笑虽然不用花钱买,不必向人借,却需要“投入”。常和爱笑的人相处,置身其中立马受到感染;注意搜集整理引人发笑的笑话、幽默等资料,品味其间自是忍俊不禁;只要有时间,尽可能去欣赏喜剧、相声之类让人发笑的艺术,使自己多笑几声。

    ⑦朋友,今天你微笑了吗?

(摘选自《大众科学》,有删改)