Final answer:
Automatic transmissions in modern vehicles automatically manage downshifting, optimizing for fuel efficiency and reducing emissions. The transition from kinetic to static friction explains why a car stops with a jer_k if the brake pedal is not slightly released before stopping completely.
Step-by-step explanation:
With modern automatic transmission technologies such as 7+ speeds, dual clutch transmissions (DCTs), and continuously variable transmissions (CVTs), the best time for an operator to downshift is largely managed by the vehicle's own computer systems. These advancements have made vehicles more fuel-efficient and reduced CO2 emissions. Operators don't need to worry about the exact timing of gear changes in typical driving situations since the system is designed to optimize the gear shifts for performance and fuel economy.
When it comes to the relationship between static and kinetic friction in the context of driving, this can be observed when braking. If you do not let up slightly on the brake pedal as you come to a stop, the car will likely stop with a je_rk due to the transition from kinetic (moving) to static (stationary) friction. By easing off the brake pedal, the transition between kinetic and static friction is more gradual, resulting in a smoother stop.