## Physics: Principles with Applications (7th Edition)

$-3.2 \times 10^{5} J$.
The net work done on the car is the change in its kinetic energy, by equation 6–4. The final KE is zero. The initial speed is 26.4 m/s. $$W = \Delta KE = 0-\frac{1}{2} mv^{2}$$ $$W = -\frac{1}{2} (925 kg)(26.4 m/s)^{2}=-3.2 \times 10^5 J$$ The work is negative because the car slows down. The answer is rounded to two significant figures.