Question

A particle moves along a straight line such that it's displacement x at any time t is given by x=t3- 6t2 + 3t + 4 m . Find the velocity, when the displacement is zero

Answer 1

first find out the roots of the given equation. you'll get values of the at which displacement is 0.
then differentiate x w.r.t t and you'll get velocity. place the values of t which you got in the first step in the expression for velocity.
you'll get the velocity when displacement is 0.

hope it helps
the mechanic
tony