At 3000 RPM, how quickly do the valves operate, opening and closing?

The correct choice indicates that at 3000 RPM (revolutions per minute), the valves in a small engine operate, opening and closing, in 1/50 of a second. To understand this, it’s important to first convert the engine speed from RPM to cycles per second (Hertz).

At 3000 RPM, the engine completes 3000 revolutions in one minute, which is equivalent to 3000/60, or 50 revolutions per second. Since typical four-stroke engines require two revolutions for each complete cycle of opening and closing the valves (one revolution for intake and one for exhaust), we can divide the cycles per second by two. Therefore, at 3000 RPM, the valves are actually completing one full cycle every 1/50 of a second.

This cycle time corresponds precisely with how quickly the valves open and close, thus confirming that the selected answer is grounded in the proper understanding of engine operation dynamics and time management based on rotation speed.