A particle is moving in a straight line. The variation of position $ x $ as a function of time $ t $ is given as: $ x = t^3 - 6t^2 + 20t + 15 $. The velocity of the body when its acceleration becomes zero is:
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To find when a particle reaches maximum or minimum velocity, set the acceleration \( a = 0 \) and solve for \( t \), then substitute \( t \) in the velocity equation.