问题 问答题

如图所示,粗细均匀的U形管竖直放置,左端封闭,右端开口,左端用水银封闭着长L=10cm的理想气体,当温度为27℃时,两管水银面的高度差△h=2cm.设外界大气压为1.0×105Pa(即75cmHg).为了使左、右两管中的水银面相平,求:

(ⅰ)若对封闭气体缓慢加热,温度需升高到多少℃?

(ⅱ)若温度保持27℃不变,需从右管的开口端再缓慢注入多少高度的水银柱?

答案

(ⅰ)对于封闭气体:

初态:P1=P0-△h=75-2=73(cmHg),V1=LS=10S,T1=300K;

末态:P2=P0=75cmHg,V2=(L+0.5△h)S=12s,T2=?;

根据理想气体状态方程:

P1V1
T1
=
P2V2
T2

代入数据

73×10
300
=
75×11
T2
,从中求得T2=339K,t2=T2-273=66℃

(ⅱ)气体作等温变化,

P3=P0=75cmHg,V3=L3S

根据玻意耳定律:P1V1=P3V3

代入数据73×10=75×L3,从中求得L3=9.73cm,即闭管水银柱上升了0.27cm,

所需注入的水银柱长为H=(2+2×0.27)cm=2.54cm

答:(ⅰ)若对封闭气体缓慢加热,温度需升高到66℃;

(ii)若温度保持27°C不变,需从右管的开口端再缓慢注入2.54cm高度的水银柱.

阅读理解

Most recently, it’s very common in students who need a parent present for job interviews. Naturally, it’s easy to blame the students in these situations, but the bigger problem is us. We—as parents—are so eager to shelter our kids that we fail to realize that this in itself is harming them.As the mother of two young sons, I have to remind myself constantly that the biggest responsibility I have as a parent is to help them develop the skills needed to live in, to live without me.So, I’ll let them fail.

I’ll let them fail because as long as they are safe and warm inside their comfort zones, they will never grow.And failure — along with loss, heartbreak, disappointment, etc.— will be part of growth for them.Call me the anti-tiger mom, but leaving them alone, is my way of helping them become equipped to fit in this world as we know it today.From terrorism and seemingly endless natural disasters, to our national debt and beyond, if we expect the next generation to stand up to the very real problems of our time, we need to stop feeding them and start teaching them how to fish.

My children now are becoming little masters of compromise, but they try to negotiate (协商) everything now.It’s a small price to help them learn a skill they’ll use for the rest of their lives, including when I don’t accompany them on job interviews.

小题1:Why do parents accompany their kids on job interviews?

A.Because they want to protect their kids from difficulties.

B.Because they think they can help them on the questions.

C.Because their kids are too shy to attend interviews.

D.Because their kids strongly request them to do so.小题2:According to the author, what is beneficial to kids’ development?

A.Sheltering them.

B.Keeping them safe.

C.Leaving them alone.

D.Blaming them.小题3:Why does the author stress failure in kids’ life?

A.To make them stronger than other kids.

B.To help them grow in this tough world.

C.To help them develop all social skills.

D.To make them learn to compromise.小题4:Which of the following might be the best title for die text?

A.Never Shelter Your Kids

B.Let Your Kids Fail

C.Be Eager to Grow Up

D.Live Without Parents

单项选择题