## Fundamentals of Physics Extended (10th Edition)

$a_{(4)}=-42\frac{m}{s^2}$
As $v=\frac{dx}{dt}=6t-6t^2$, $a=\frac{dv}{dt}=6-12t$ Next, we substitute $t=4$ in the expression to find the value of $a$ at $t=4s$: $a_{(4)}=6-12(4)=6-48=-42\frac{m}{s^2}$