Mathematics

Problem

The position of a particle moving along a line is given by

s(t)=t^{3}-6t^{2}+9t+2

, where

t

is measured in seconds and

s

in meters. On the interval

0\le t\le 4

, at which time(s) does the particle change direction? a)

t=2

only b)

t=1

only c)

t=1 \text{ and } t=3

d) The particle never changes direction on

[0,4]