A particle's position is $s(t)=t^3-9t^2+24t+1$ meters at time $t$ seconds. Which statement best describes its motion at $t=4$ seconds?

Core Concept

Velocity is $v(t)=3t^2-18t+24$, so $v(4)=48-72+24=0$. Since $a(4)=6(4)-18=6>0$, the velocity turns positive just after $t=4$, so the particle moves right.