Final answer:
D. the gears do not grind. When double clutching is performed correctly and RPMs are matched, it prevents gears from grinding. This technique is essential for a smoother gear transition and can extend the life of the gearbox. Modern transmissions aim to automatically achieve this smoothness while improving fuel economy and reducing emissions.
Step-by-step explanation:
When double clutching is done correctly, and the RPMs are matched during the shift, the correct answer is D. the gears do not grind. Double clutching is a technique used in manual transmission vehicles where the driver presses the clutch pedal twice, once to disengage the current gear and then again when engaging the new gear. The process of matching the engine's RPM (revolutions per minute) to the speed of the transmission gear is crucial because it allows the gear teeth to align without the harsh friction that causes grinding. This method not only ensures a smoother transition between gears but also can help prevent damage to the gearbox over time.
Transmission technologies like 7+ speeds, dual clutch transmissions (DCTs), and continuously variable transmissions (CVTs) are designed to improve fuel economy and reduce CO₂ emissions. While these modern transmission systems often handle gear changes automatically and with much efficiency, the principles of smooth transitions and matching engine speed to gearbox speed are similarly important in avoiding unnecessary wear and maintaining optimal performance.
Nearly all conventional piston engines have flywheels on them to smooth out engine vibrations caused by the thrust of individual piston firings. This is because the flywheel acts as a rotational mass, providing inertia to keep the engine running smoothly between power strokes and minimizing vibration, which is essential for both engine longevity and performance.