外的笔画顺序是:____
文中引用徐霞客赞美黄山的名句:“五岳归来不看山, 。”其中“五岳”是指东岳( ),南岳( ),西岳( ),北岳( ),中岳( )。
American people like to say "Thank you " or say something kind when others help them.People of many countries do so,too.It is a very good habit. You should say"Thank you'when someone passes you the salt on the table,when someone walking ahead of you keeps the door open for you and when someone says you always do your work well or you have a nice thing or your city is very beautiful.“Thank you”is used not only between friends,but also between parents and children,brothers and sisters. “Excuse me”is another short sentence they use.When you hear someone says“Excuse me”behind you,you know that someone wants to walk past you without touching you.It’s not polite to break(打断)others when they are talking.If you want to speak to one of them。say‘Excuse me’first,and then begin talking.You should also do so when you begin to cough or make any noise before others.Let‘s learn to say‘Thank you’and‘Excuse me’.
在水下气泡内空气的压强大于气泡表面外侧水的压强,两压强差△p与气泡半径r之间的关系为△p= 2σr ,其中σ=0.070N/m.现让水下10m处一半径为0.50cm的气泡缓慢上升,已知大气压强p0=1.0×105Pa,水的密度ρ=1.0×103kg/m3,重力加速度大小g=10m/s2.
①求在水下10m处气泡内外的压强差;
②忽略水温随水深的变化,在气泡上升到十分接近水面时,求气泡的半径与其原来半径之比的近似值.
名著阅读。