问题 计算题

高压锅是家庭厨房中常见的炊具,利用它可以将食物加热到100℃以上,它省时高效,深受消费者欢迎。

(1)为了防止出气孔堵塞致使高压锅发生爆炸的危险,放气孔是它的第二道安全防线。放气孔封口是易熔片(熔点较低的合金材料),试说明采用易熔片的物理道理;

(2)小明测得家中高压锅出气孔的直径为3mm,压在出气孔上的安全阀的质量为35g,取g=10N/kg,计算安全阀自重对出气孔处气体所产生的压强;

(3)当高压锅内气压增大到某一值时,锅内气体就能自动顶开安全阀放气。在外界为标准大气压的环境下,该高压锅内的气体能达到的最大压强是多少?对照图所示水的沸点与气压的关系图线,说明利用这种高压锅烧煮食物时,可以达到的最高温度大约是多少?

答案

(1)温度升高达到熔点,易熔片熔化,气体漏出,内部压强减少

(2) 4.9×104 Pa

(3)1.49×105Pa;113(114)℃

阅读理解

Catherine and I were on our way to our nephew’s birthday party one rainy Saturday morning, driving along what some people call moose(驼鹿) alley. It was early, there were few other cars on the road and we were looking forward to a good day with the family. Suddenly, a moose rushed across our path. Fortunately, a quick swerve(突然转向) to the other lane prevented a full impact, with only a small collision on the right side of our car ripping off the mirror and knocking the moose to the pavement.

By the time I stopped and looked back in my rear view mirror, the moose was getting up. It ran into the bush. Shaken but unharmed, we both looked at each other shocked by what had happened. We knew that moose accidents had claimed many lives throughout the years, and that we had been very fortunate to escape with no personal injury or worse. After a quick check of our vehicle, we drove off.

Even though the moose accident lasted just a few seconds, we still remember it to this day. Why?

We had often talked about the frailty of life, the here today and gone tomorrow potential we all face, but it had never felt so real. And it wasn’t that we hadn’t had friends, relatives and colleagues die before, it was that this experience was much more personal. In a matter of seconds, lives can easily change.

The effect of that one near miss with death has been positive, and made us appreciate life. Each one of us has only a limited time on this Earth; no one can predict when your time will end. We should give thanks for each day, to see the sun rise again, and to know that you can accomplish and assist others to appreciate their life if they are caught in the “poor-me” syndrome(综合症状).

小题1:What can we learn about the accident form the first two paragraphs?

A.Fortunately, they didn’t hit the moose.

B.They themselves were slightly injured.

C.Many people have died from similar accidents.

D.The author should be blamed for the accident.小题2:What did the accident teach the author?

A.Being open to unexpected turns in life is important.

B.Life is long if you know how to use it.

C.Life is measured by thoughts and actions, not by time.

D.Life is unpredictable, so we should treasure every moment.小题3:How should we spend every day according to the author?

a. being thankful and helpful

b. appreciating the natural beauty of the world

c. being confident

d. making every effort to succeed

A.ab

B.bc

C.abc

D.bcd

单项选择题