问题 计算题

电动汽车越来越受到人们的青睐,电动版朗逸是大众汽车首款完全在中国开发的车型.它已在北京车展上和世人见面.朗逸电动车由安装在车头部位的电动机驱动,电动发动机的最大功率为85kW,持续输出功率是50kW;该车具有出色的动力表现,从静止加速到100km/h用时11s,运动路程为165m.电池系统是由锂离子电池单元组组成,容量为26.5kW·h,充满电连续行驶里程(60km/h等速状态下)为l50km;电池可以通过家用220V电源直接充电,充满电所需时间为6h.请根据以上信息,求:

(1)电池在家用电源下的充电电流;

(2)电动汽车充满电连续行驶的时间;

(3)电动汽车从静止加速到100km/h的过程中的平均速度;

(4)在持续输出功率下,当电动汽车以l00km/h的速度匀速行驶时,电动机所提供的牵引力.

答案

解:(1)电池容量即为电池所储存的电能,由题意知:电池的容量

W=26.5kW·h=2.65×104W·h

充电电压U=220V,充电时间t=6h,由W=UIt得:充电电流:

I==≈20A.

(2)已知路程s=150km,速度v=60km/h,由v=得:汽车连续行驶的时间

t===2.5h.

(3)已知路程s=165m,加速时间t=11s,由v=得:汽车的平均速度:

===15m/s

(4)汽车持续输出功率P=50kW=5×104W,电动汽车速度v=l00km/h,汽车匀速行驶时的牵引力

F===1800N

单项选择题

Fear seems to be the dominant mood of the moment. Hurricanes, tidal waves, floods, earthquakes and terrorism this year have all brought with them not only appalling scenes of devastation, death and suffering, but also outrage at the lack of preparations to avoid or cope with these disasters. Now even the birds of the air are a threat, we are told. That migrating flock visible On the horizon at sunset, once a consoling reminder of the eternal rhythms of nature, could be carrying the virus which might soon kill tens of millions of people.

Given the many fingers pointed at governments in the wake of other disasters this year, it is hardly surprising that they are scrambling to respond to the threat posed by avian influenza. After confirmation this week that the HSN1 strain of bird flu, which has been spreading quickly in Asia, had been discovered in Romania and perhaps Greece, European Union foreign ministers convened an emergency meeting. President George Bush, still smarting from a torrent of criticism of his government’s clumsy response to Hurricane Katrina, has promised to rush out emergency plans for dealing with an outbreak of pandemic flu which have been stalled for years. Countries around the world are hurrying to stockpile the only current antiviral drug, Tamifln, which might be effective in saving lives in any pandemic or curbing its spread. The World Health Organisation is calling for an internationally coordinated effort. Health ministers from around the globe are due to meet next week in Canada to discuss what steps to take.

Is any of this eff6rt justified Or are politicians simply helping to feed public panic, and then covering themselves by promising to spend lavishly against a threat which may never materialize and to reduce a risk which they do not understand To ask these questions is not to counsel complacency, but to apply the kind of test which is required in any kind of disaster planning, not least because the world is an inherently dangerous place and it is impossible to plan against every possible disaster. With the media full of warnings of impending mass death, an overreaction is all too possible.

It can be inferred from the first paragraph that ()

A. p resentment resulted from the lack of preparations to cope with recent disasters

B. the dominant mood of the moment resulted in the appalling scenes of devastation

C. tens of millions of people could carry the virus on the horizon

D. reminder of the eternal rhythms of nature emerged at sunset to avoid these disasters

多项选择题