The most important result from last time was that if you took this r, and you took two derivatives of this to find the acceleration, d^2 r over dt^2, try to do this in your head.

上节课最重要的结论,就是如果你把 r 写成这样,对 r 求两次导就能得到加速度,d^2 r / dt^2,心算一下

耶鲁公开课 - 基础物理课程节选

Researchers also found that balls inflated at higher pressure hit the head with greater acceleration, even when kicked at the same speed.

WSJ: Soccer 'Header' Impact Likened to Hard Punch

About ten minutes later, he has a 98-g acceleration to the front of his head.

NEWYORKER: Offensive Play

The commission's head honcho recently announced new actions to the Broadband Acceleration Initiative, clarifying technical provisions within the Middle Class Tax Relief and Job Creation Act of 2012 that should make mobile broadband deployment a little easier.

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