m1+m1+……myN ∑ (7-11) m1+m2+……mNy In terms of components Eq(-11) can be written as (7-12) nn Taking the derivative of Eq(7-11) (7-13) M Differentiating once again mm a M Or ma=∑mnan=∑F+∑2+…∑F(7-15)In terms of components, Eq(7-11) can be written as Taking the derivative of Eq(7-11) (7-13) Differentiating once again: (7-14) cm =  n n m x M x 1 cm =  n n m y M y 1 cm =  n n m z M z 1 → → cm =  n n m v M v 1 → → cm = mn an M a 1     → → → → → = = + +  Or M acm mn an F1 F2 FN (7-15) → → → → =  + + + + = n n N N N c m m r m m m M m r m r m r r 1 1 2 1 1 2 2  (7-11) (7-12) , ,