1 The displacement of a particle from its equilibrium position is \(x\) metres at time \(t\) seconds. The motion of the particle obeys the differential equation $$\frac { \mathrm { d } ^ { 2 } x } { \mathrm {~d} t ^ { 2 } } = - 9 x$$ Calculate the period of its motion in seconds.
Circle your answer.
[0pt] [1 mark]
\(\frac { \pi } { 9 }\)
\(\frac { 2 \pi } { 9 }\)
\(\frac { \pi } { 3 }\)
\(\frac { 2 \pi } { 3 }\)