来自《耶鲁大学开放课程：基础物理 第3集 第3集》

• 
  
  out comes the elliptical motion of the planets.
  就得到了行星作椭圆运动的方程
• 
  
  We'll come back to that,
  我们等下回头再讲
• 
  
  but you have to understand the structure of Newtonian mechanics.
  不过你们要理解牛顿力学的体系框架
• 
  
  Generally, any mechanics will require knowledge of the force.
  基本上任何力学都要先了解什么是力
• 
  
  Now, I'm going to add one more amendment.
  现在我再稍微修改一下
• 
  
  You don't have to write in your notebook,
  你不必记下这个
• 
  
  but you've got to remember.
  不过你要记住
• 
  
  Maybe you'll put a little T and circle it.
  也许你要标注一个带圈的 T
• 
  
  Let me write it here.
  我写在这边
• 
  
  FT means the total force on a body.
  FT 表示物体所受的合力
• 
  
  You've got many forces acting on a body.
  很多力同时作用在物体上
• 
  
  The acceleration is controlled by the sum.
  加速度由合力决定