16). Harman is driving his 2500 kg car at 25 m/s. As he approaches a red light, he steps on the brakes and his car comes to rest after 56 m. Determine the force of friction as the car breaks.

The force of friction consumes the kinetic energy of the car.

Now, let F be the force of friction, make a following equation of energy conservation

$$\mathrm{F}\cdot 56 \mathrm{m}=\dfrac{1}{2}\cdot (2500 \mathrm{kg}) \cdot (25\mathrm{m/s})\:.$$

By solving that equation, we can determine the force of friction F.