4. A truck has a drag coefficient based on frontal area of $C_D = 0.86$. The truck has a mass of 12,750 kg and a frontal area of 10.5 m$^2$. If the truck is traveling at constant speed on a level road, the forces retarding its forward progress are the drag and the rolling friction. The force due to rolling friction can be written as
$F_{rf} = Wf_r(1 + \frac{V}{V_0})$
where $V$ is the truck speed in m/s, $V_0 = 30$ m/s and $f_r$ (the coefficient of rolling resistance) is approximately 0.008 for a truck on concrete or asphalt. Plot the total power the engine must supply as a function of truck speed, $V$. Comment on the relative importance of drag and rolling friction in the fuel consumption of the truck.
Figure for problem 4.
