问题 计算题

随着国民经济的发展,汽车已走进家庭。一辆小轿车以某一速度在平直路面上匀速行驶100km,消耗汽油10L。若这些汽油完全燃烧放出的热量有30%用来驱动汽车做有用功,所用汽油的热值为4.6×107 J/kg,密度为0.7×103kg/m3,求:

(1)这些汽油完全燃烧放出的热量;

(2)这辆轿车以该速度匀速行驶时受到的阻力。

答案

解:

(1)ρ= m/V,m=ρV=0.7×103 kg/m3×10×10-3m3= 7kg,Q= mq = 7kg×4.6×107J/kg = 3.22×108J;

(2)W= Q×30% = 3.22×108J×30% = 9.66×107J,W=Fs,F= W/s 966N

∵车匀速直线行驶

∴f= F= 966N。

完形填空

根据短文内容,从短文后的选项中选出能填入空白处的最佳选项。选项中有两项为多余选项。

Writing a book takes a strong will, hard work, and, most importantly, time. There’s no easy way to finish your first book, but we’ve got some tips that might help you.

76. 小题1: _    __ Find a place convenient(方便)and comfortable for you. Make sure you can put your heart into your writing at this place.

77. 小题2: _    __ Make sure you have everything you need around you. Have plenty of pens, paper for printing if you’re using a computer, or notebooks if you’re writing by hand. Make sure you’ve got them near you, so you don’t have to keep getting up to find things.

Keep away from distractions(分心的东西). Put down your magazine, turn off your mobile phone, cut off the Internet …

Make time. 78. 小题3: _    __ You can pick a time when your house is quiet — whether you get up an hour earlier or go to bed an hour later. You should soon find yourself in the habit, and you may even find your hour turns into three.

79. 小题4: _    __ When you’re not at your desk, it doesn’t mean you shouldn’t be thinking. Carry a notebook on you at all times. 80. 小题5: __    _ You may only use 5% of them, but that 5% will be well worth the effort.

A.Try and set aside an hour a day, or at least a few hours a week.

B.Find somewhere to write.

C.Only those who work hard can finish their writing.

D.Keep your tools near you.E. Don’t stop thinking.

F. Learn how to collect useful information.

G. Write down all your ideas, no matter how weak they seem.

单项选择题