The average acceleration of an object is calculated as the final speed minus the initial speed divided by the elapsed time.
So:
[tex]a = \frac{V_f-V_0}{T_2-T_1}[/tex]
Where
[tex]V_f[/tex]= final speed
[tex]V_0[/tex] = initial speed
[tex]T_2-T_1[/tex] = elapsed time.
Thus:
The acceleration of the cyclist is:
[tex]a = \frac{8-0}{3}[/tex]
a = 2.667[tex]m / s ^ 2[/tex]
The acceleration of the car is:
[tex]a = \frac{30-0}{8}[/tex]
a = 3.75 [tex]m/s^2[/tex]
The average acceleration of the car is higher than the average acceleration of the cyclist.
