书籍详情
格式
Kindle
页数
24
语言
英语
已发布
Jan 1, 2014
出版商
The Child's World
ISBN-10
1631431307
ISBN-13
9781631431302
描述
Readers learn how this simple machine makes it easier to lift, lower, and open things. They learn the three types of levers: first-class, second-class, and third-class. By the end of the book, readers know the difference between complex and simple machines and how levers are used in everyday life to make work easier.