(a)[1]
State the meaning of velocity.
(b)[2]
The drag force $F_D$ on a car moving with speed $v$ along a straight horizontal road is given by $F_D = v^2 A k$, where $k$ is a constant and $A$ is the cross-sectional area of the car. Determine the SI base units of $k$.
(c)[3]
In part (b), the value of $k$ in SI base units is $0.24$, and the cross-sectional area $A$ of the car is $5.1\,\text{m}^2$. The car is moving at constant speed along a straight road, and the engine output power is $4.8 \times 10^4\,\text{W}$. Take the engine output power to be equal to the rate at which the drag force $F_D$ does work against the car. Determine the speed of the car.