The force opposing the motion of a car is proportional to the square of the car’s speed. At a speed of $20.0\,\text{m s}^{-1}$, the magnitude of the force is $800\,\text{N}$. What useful output power must be supplied by the car’s engine to keep the car moving at a steady speed of $40.0\,\text{m s}^{-1}$?
- A$32\,\text{kW}$
- B$64\,\text{kW}$
- C$128\,\text{kW}$
- D$512\,\text{kW}$