We are given the expression for the distance 'x' in terms of 't'.
We need to first differentiate x(t) to find an expression for the velocity in terms of 't'
[tex]x(t) = 30+11.7t-0.0450t^3[/tex]
[tex] \frac{dx}{dt} = 11.7(1)t^{1-1}-(0.0450)(3)t^{3-1}[/tex]
[tex]v= \frac{dx}{dt}=11.7-0.135t^2 [/tex]
The value of v when t = 8
[tex]v(8)=11.7-0.135(8)^2 = 3.06m/s[/tex]
