问题 解答题

一振子从一点A开始左右来回振动8次,如果规定向右为正,向左为负,这8次振动记录为(单位mm):

+10,-9,+8,-6,+7.5,-6,+8,-7.

(1)求停止时所在位置距A点何方向,有多远?

(2)如果每毫米需时0.02秒,则共用多少秒?

答案

(1)根据题意可得:向右为正,向左为负,由8次振动记录可得:10-9+8-6+7.5-6+8-7=5.5,

故停止时所在位置在A点右边5.5mm处;

(2)一振子从一点A开始左右来回振动8次,共10+9+8+6+7.5+6+8+7=61.5mm.

如果每毫米需时0.02秒,故共用61.5×0.02=1.23秒.

阅读理解

Mr. Jenkins is a farmer. One day he drove his truck to town and on the way his truck knocked down a boy and hurt him. He took the boy to a hospital and he paid a lot of money for that, but the boy’s parents wanted to get more money from him, so they said their son couldn’t lift(举起) his right arm above his head.

Mr. Jenkins’ lawyer came and asked the boy some questions. “Now, my boy,” he said, “Mr. Jenkins’ truck knocked you down in the street.”“Yes, sir,” he said. “And you can’t lift your right arm now?”“Yes, sir,” he said. “Could you show me how high you can lift your right arm?” Slowly the boy lifted his right arm before his nose. “Poor boy,” said the lawyer, “And how high could you lift before the accident?”“Oh, I could lift it very high.” Said the boy, and the right hand went up high above his head.

小题1:Mr. Jenkins’ truck knocked down ________.

A. a lawyer            B. a boy’s father         C. a boy

小题2:The boy’s parents wanted to get ________ from him.

A. more trucks              B. more money          C. more monkeys

小题3:Mr. Jenkins’ lawyer asked the boy to ______.

A. ask some questions       B. answer some questions    C. lift his left arm

小题4:The boy said he couldn’t lift his _________ now.

A. right arm                B. left arm            C. right foot

小题5:There is _______ wrong with the boy.

A. something              B. anything                C. nothing

单项选择题