Scientific Explorer -- Movement, Force and Energy

Author: Edited by [USA] Padilla, Hu Yueming, Cao Zengjie Translated by
Publisher:
Publish Date: 2003-02-01
Features: Widely used comprehensive science textbook in American middle schools, the best reference book for new curriculum standards, new concepts, and new learning methods. Explore the mysteries of science, guide inquiry-based learning, emphasize knowledge, skills, and methods equally, with hands-on and brain-stimulating fun. Whether an object is in motion or not does not depend on how it looks. A book on the table seems to be at rest relative to the floor under the table. However, if you compare the book to the Sun, the book is actually moving at high speed. Earth and the Sun are different reference frames. A reference frame is an object used to determine whether another object is in motion. If the relative position of an object changes with respect to a reference frame, then the object is in motion. A reference frame is assumed to be stationary or at rest in advance.