A particle is moving in one dimension (along x axis) under the action of a variable force. It's initial position was 16 m right of origin. The…

A particle is moving in one dimension (along $\displaystyle x$ axis) under the action of a variable force. It's initial position was $\displaystyle 16$ m right of origin. The variation of its position $\displaystyle (x)$ with time (t) is given as $\displaystyle x=-3 \mathrm{t}^3+18 \mathrm{t}^2+16 \mathrm{t}$, where $\displaystyle x$ is in m and t is in s. The velocity of the particle when its acceleration becomes zero is $\displaystyle \_\_\_\_$ m/s.