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