一支长为130米的队伍做匀速直线运动,速度为5米/秒,方向与列车同向.列车长150米,以54千米/时的速度匀速前进.问列车要越过这列队伍,需多长时间?

题目

一支长为130米的队伍做匀速直线运动,速度为5米/秒,方向与列车同向.列车长150米,以54千米/时的速度匀速前进.问列车要越过这列队伍,需多长时间?
“有人说4克镁条在1克氧气中点燃,完全燃烧后生成5克氧化镁,符合质量守恒定律.”这句话错在哪里?
大气中含量最多的元素是什么?
以下各组物质都属于混合物的是（）
（A）海水和蒸馏水
（B）液氧和天然气
（C）碘酒和纯盐酸
（D）胆矾和空气
（E）煤和石油
（F）食醋和牛奶
已知P是正方形ABCD内一点,且点P到ABC三个顶点的距离分别为1、2、3,求这个正方形的面积.
翻译句子：
I rarely buy a morning paper.
He is the Newton of this age.
The robber and murderer was killed.
The earth turns itself from west to east.
Bob has a deep love for the Chinese art.
The public showed great interest in Russian films.
Is there any flower on the table?
We had supper at the Greens and we liked the dinner very much.
We have many subjects at school.i like Chinese,maths and English best.
Do you know this is a one-way street?
If I fail this time,I'll try it a second time.
One rainy day,a friend of mine came to see me.
We are going to have a party on New Year's Eve.
We pay the rent by the month.
people asked.
First someone took picture of the bridge.
The tenth five-year plan is now being carried out.
I will wait for you at the school gate at two o'clock this afternoon.
What's the population of China?It's about 1,300 million.
There aren't any better 200-metre runners than him in our school.
Eighty percents of the population of our country are farners.
China has an area of 9.6 million square kilometres.
He has traveled three-fourths of Beijing.
Will you take Bus No.13 or the No.18 bus?
Do you know what a quarter to eight is?It's fifteen to eight.
Shortly after the accident,two dozen policemen were sent to hte spot to keep order.
Thursday is the fifth day of the week.
He is staying in Room 201.
）
更正一下Shortly after the accident,two dozen policemen were sent to hte spot to keep order.中的hte应该是the,打太快了~
呃,第一题的确就是这样的.标答上写：28秒.（天知道这个答案怎么来的）
正方形面积的那一题,标答上写：5+2√2（还是不知道这个答案怎么来的.要注意哦,点A、P、C不一定同线）

答案

第一道题不会.“有人说4克镁条在1克氧气中点燃,完全燃烧后生成5克氧化镁,符合质量守恒定律.”这句话错在哪里? 根据质量守恒定律,2Mg + O2 === 2MgO 48 32 80镁和氧气和氧化镁的质量比为4...