Answer
$a_{max}=5.7\times10^2\frac{m}{s^2}$
Work Step by Step
We know that $a_{max}=A\omega^2$
and $\omega=2\pi$$f$=$2\times3.14\times120=754\frac{rad}{s}$
put the values in the very first equation
$a_{max}=(1mm)(754)^2$
As we know $1mm=10^{-3}m$
so
$a_{max}=10^{-3}\times(754)^2$
$a_{max}=10^{-3}\times568516$
$a_{max}=10^{-3}\times5.68516\times10^5$
$a_{max}=5.7\times10^2\frac{m}{s^2}$
