人骑自行车下坡，坡长L=500m，坡高h=8m，人和车的总质量为100kg，下坡时初速度为4m/s，人不踏车的情况下，到达坡底时的车速为10m/s，g=10m/s2,则下坡过程中阻力所做的功为（）

题干

人骑自行车下坡，坡长L=500m，坡高h=8m，人和车的总质量为100kg，下坡时初速度为4m/s，人不踏车的情况下，到达坡底时的车速为10m/s，g=10m/s²,则下坡过程中阻力所做的功为（）

A：-4000J

B：-5000J

C：-3800J

D：-4200J

上一题下一题 0.0难度选择题更新时间:2015-06-11 07:35:27

C

Zhang Hong在学校参加了一个English Club, 从那以后，她改变了很多。请你结合下面所给的提示，写一篇约80个单词的英语短文。

	In the past	Now
Personalities (性格)	shy, quiet, get nervous easily, not dare to speak in public	brave, outgoing, kind of active…
Hobbies	Reading and watching TV	reading, singing ,dancing, making friends, playing badminton…
Abilities	Doing well in reading	Be good at reading, dancing, singing, communicating and sports.

要求: 1. 覆盖要点，可适当增加情节；2. 80词左右，开头与结尾已经给出，不计入总词数。

Joining a club sometimes changes a person greatly.

People sure change all the time, right? What we should do is to learn from Zhang Hong? Change ourselves and choose to be the best of ourselves.

鞋的尺码（单位：cm）	22.5	23	23.5	24	24.5
销售量（单位：双）	3	6	12	9	8