【简答题】–Do you like swimming in a lake? –_____. I think swimming in big rivers is a lot more interesting. A.No problem B.Not so badly C.Probably not D.Not all that much
【简答题】由流体力学知,理想流体的完整方程组由Euler型运动方程 (1.3.1) 和连续性方程 (1.3.2) 以及物态方程 p=f(ρ),(1.3.3) 组成,其中方程(1.3.1)应该看作三个分量υ x ,υ y ,υ z 的方程;υ,p,ρ分别为流速、压力和密度;F为单位质量上所受外力.试导出当外力F=0时,声波在空气中传播所满足的声波方程.