题目

一枚静止时长30m的火箭以3 的速度从观察者的身边掠过，观察者测得火箭的长度应为多少？火箭上的人测得火箭的长度应为多少？如果火箭的速度为光速的一半呢？ 答案：解：根据狭义相对论得火箭上的人测得火箭的长度为30m，若v=3km/s≪c，地面上的观察者测得火箭的长度 L=L01−v2c2≈L0=30m 所以地面上和火箭上的观察者测得火箭的长度相同，若火箭以0.5c的速度飞行，根据长度的相对性有 L=L01−v2c2地面上的观察者测得火箭的长度为 L=30×1−(0.5cc)2≈26mAs is known to all, in daily conversation modern people like to use simple words and simple sentences, especially some sentences with some parts left out. Here is an interesting example from the conversation between Henry, a fisherman, and his wife Sylvia. Do you know what they are talking about?Sylvia: Going?Henry: Been.Sylvia: Any?Henry: Some.Sylvia: Big?Henry: Small.1.Which of the following is TRUE according to the conversation? A.Sylvia got some fish for Henry.        B.Henry didn’t catch any fish.C.Sylvia has cooked some fish.          D.Henry has just been back with some fish.2.The text is mainly about           .A.catching fish in the sea                         B.spending holidays C.short forms in daily talks                     D.joy in daily life3.The writer wants to tell us simple words and sentences are ________ in daily conversation. A.terrible            B.popular                 C.out of date     D.out of sight