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a
→



(
t
)
=





d


2





r
→



(
t
)



d


t

2





=





r
→


¨



(
t
)


{\displaystyle {\vec {a}}(t)={\frac {\mathrm {d} ^{2}{\vec {r}}(t)}{\mathrm {d} t^{2}}}={\ddot {\vec {r}}}(t)}

