Answer
a) $240$ mm
b) $60$ mm/s
c) $20$ mm/s^2
Work Step by Step
$s=10t^2+20$
a)
$s|_{1s}=10(1)^2+20=30$ mm
$s|_{5s}=10(5)^2+20=270$ mm
$\Delta s = 270-30=240$ mm
b)
$\Delta t = 5-1=4$ s
$v_{avg}=\frac{\Delta s}{\Delta t}=\frac{240}{4}=60$ mm/s
c)
$a=\frac{d^2s}{dt^2}=20$ mm/s$^2$