节流孔板前的直管段一般要求为()D,孔板后的直管段一般要求为()D。为了正确测量,孔板前的直管段一最好为()D。
参考答案:10;5;30~50
读一读,选一选。
My name is John. I live in China now. My mom and dad are in Canada. I have long legs and arms. I have
a big nose and little ears. My hair is brown. My eyes are blue. My favourite colour is black. I have a black shirt
and a black coat. My pants and shorts are black, too.
Here are many restaurants. I like to eat Chinese food. My favourite Chinese food is dumplings. Chinese
food doesn't have too much sweet food, but it's very delicious. In China I have many new Chinese friends. I
feel happy here.
1. John __________.[ ]
A. has a little nose
B. has blond hair
C. is in China
D. is short
2. Where do his mom and dad live? [ ]
A. In the school.
B. In the U. S.
C. In China.
D. In Canada.
3. What colour does John like?[ ]
A. Green.
B. Black.
C. Brown.
D. Red.
4. What's his favourite Chinese food?[ ]
A. Chinese meat.
B. Chinese fruit.
C. Dumpings.
D. Noodles.
5. How does he feel now?[ ]
A. He feels happy.
B. He feels sad.
C. He feels tired.
D. He feels hot.
A.此时小球处于平衡状态
B.若细绳断裂,小球将失去惯性
C.若细绳断裂,小球将做自由落体运动
D.细绳断裂后,小球在空中运动处于完全失重状态