For this guy, F = ma will be 10 - f = 3a.

对这个物体,F = ma 就是 10 - f = 3a

耶鲁公开课 - 基础物理课程节选

What's the difference between saying F = -kx and F = ma?

= -kx 与 F = ma 的区别在哪里

耶鲁公开课 - 基础物理课程节选

The free-body diagram, it says you can pick any one body that you like and apply F = ma to it, provided you identify all the forces acting on that body.

所谓隔离法,就是说你可以任意 选取一个物体,分析出它所受的所有力后,单独对其运用 F = ma 进行计算

耶鲁公开课 - 基础物理课程节选