SAT2物理练习之What Are Forces

 　下面小编为大家整理了SAT2物理练习的内容：What Are  Forces，希望对大家的备考有所帮助。

　　Whenever we lift something, push something, or otherwise manipulate an  object, we are exerting a force. A force is defined very practically as a push  or a pull—essentially it’s what makes things move. A force is a vector quantity,  as it has both a magnitude and a direction. 　　In this chapter, we will use the  example of pushing a box along the floor to illustrate many concepts about  forces, with the assumption that it’s a pretty intuitive model that you will  have little trouble imagining.　　Physicists use simple pictures called free-body  diagrams to illustrate the forces acting on an object. In these diagrams, the  forces acting on a body are drawn as vectors originating from the center of the  object. Following is a free-body diagram of you pushing a box into your new  college dorm with force F.