2015年9月3日,中国人民抗日战争暨世界反法西斯战争胜利70周年纪念大会在北京隆重举行。据此回答下列问题。
***身穿中山装主持阅兵大典,既有革新又不失传承意味,可说用意深远,传达出中山装这一中国“政治图腾”蕴涵的开放、民主、民族复兴之意。这表明( )
A: 文化起源于人们的物质需求
B:精神产品离不开物质载体
C:文化现象实质上是物质现象
D:先进文化是一种物质力量
Mr Green is an Englishman. He teaches English well His English classes are very interesting. He likes us and we like him, too.Mr Green has two children----Mike and Nancy. Mike is eight and his sister Nancy is five. Mike goes to school but Nancy doesn't. Mr Green likes to wear a T-shirt and a pair of jeans. Football is his favorite sport. After school we often have a basketball match. Sometimes Mr Green watches and joins us. He plays basketball just for us.
①他将小球用一根细线悬挂起来,如图(a)所示,剪断细线后小球落下,如图(b)所示。
②他又将小球用两根细线悬挂起来,如图(c)所示,剪断其中的一根细线,小球发生摆动,如图(d)所示。通过实验,他的疑问得到解决根据实验现象及相关条件,小明同学归纳得出的初步结论:(选填下面对应的结论字母)
阅读短文并回答下列问题.
流体阻力液体和气体都是流体.物体在流体中运动时会受到阻力作用,该阻力叫做流体阻力,流体阻力大小跟相对运动速度大小有关,速度越大,阻力越大;跟物体的形状有关,头圆尾尖(这种形状通常叫做流线型)的物体受到的阻力较小.精确研究表明,物体在空气中低速运动时,空气阻力f阻与相对速度的关系为f阻=kv2,k为常数,且k=1×10﹣4N•s2/m2.