Remember, Newton said F = ma, but didn't tell you what value F has in a given context.

记住,牛顿只说 F = ma,但却没告诉你 F 在特定条件下的值是多少

耶鲁公开课 - 基础物理课程节选

You're only given the particle has acceleration a, and you are asked to find out what is x?

你只知道质点的加速度为a,你需要求出x是多少

耶鲁公开课 - 基础物理课程节选