Solution:

The initial kinetic energy of the car is \(K_i = \frac{1}{2}mv^2 = \frac{1}{2}(1000)(20)^2 = 2 \times 10^5\text{ J}\) and final kinetic energy is zero. Average power dissipated is the work done divided by time: \(P = \frac{\Delta K}{t} = \frac{2 \times 10^5\text{ J}}{5\text{ s}} = 40\text{ kW}\).