Resistance to the motion of an automobile consists of road friction, which is almost independent of speed, and air drag, which is proportional to speed-squared. For a certain car with a weight of 12 000 N, the total resistant force F is given by F ! 300 & 1.8v2 , with F in newtons and v in meters per second. Calculate the power 212 CHAPTER 8 POTENTIAL ENERGY AND CONSERVATION OF ENERGY (in horsepower) required to accelerate the car at 0.92 m/s2 when the speed is 80 km/h.

Potential Energy and Conservation of Energy Conservative and Nonconservative Forces ● Conservative force: The work it does is stored in the form of potential energy that can be used at another time. ○ Gravity is a conservative force ○ Friction is a nonconservative force ● Conservative forces are path independent ● Work done by a nonconservative...