题目

A、B两质点分别做匀速圆周运动，在相同时间内，它们通过的弧长之比sA:sB=2:3，而转过的角度之比φA:φB=3:2，则它们的周期之比TA:TB=______；角速度之比ωA:ωB=______；线速度之比vA:vB=______，半径之比RA:RB=______. 答案：2:3  3:2  2:3  4:9 解析:由v=得vA:vB=sA:sB=2:3，由ω=得ωA:ωB=φA:φB=3:2，TA:TB=ωB:ωA=2:3，由v=ωR得RA:RB=(vAωB):(vBωA)=4:9.阅读理解。     It was 1504,and Columbus was making another trip to the New World. Columbus and his menneeded fresh water and food after three months at sea. They saw an island and went on shore. On the island there were unfriendly Indians who refused to give food to them. Columbus' men wereafraid of the Indians, but he had a clever plan. He used sign language to tell the Indians about hismysterious (神秘的) power to turn off the light in the sky. He knew about a lunar eclipse (月蚀)the next night because the information was in his almanac (天文历书). Columbus told the Indians, " Tomorrow night I'll turn off the light in the sky." But they didn't believe him . When the eclipse began the next night ,the Indians became very frightened . They begged Columbus to turn on thelight again , and they quickly gave him all the food and water he wanted. Immediately Columbus and his men hurried back to the ship and sailed away in the moonless night.1.Columbus and his men stopped at the island because_______________.A. they wanted to meet the Indians thereB. they hoped to get supplies of food and waterC. they had never been on the island beforeD. they had planned to visit it          2.The Indians ___________ Columbus and his men.A. were glad to see       B. were kind to C. welcomed            D. were not kind to 3.Columbus ________ to tell the Indians that he had mysterious power.A. used movements of hands and expressions in his faceB. spoke in the language of the IndiansC. drew a lot of signs D. wrote in the language of the Indians4."The light in the sky " here means __________.A. the sun    B. the moon     C. the stars     D. the daylight5.The Indians gave Columbus food and water because they _________.A. believed Columbus was a man with mysterious powerB. were interested in Columbus' tripC. wanted to help Columbus D. were clever