NEIEP Mechanics Practice Exam

If a gearless machine's drive sheave has a circumference of 6 feet, approximately how many RPMs are needed to run at 800 fpm?

1. 100 RPM

2. 120 RPM

3. 133 RPM

4. 150 RPM

The correct answer is: 133 RPM

To determine the revolutions per minute (RPM) needed for a gearless machine's drive sheave to achieve a specific speed, you can use the relationship between speed (in feet per minute), the circumference of the drive sheave, and the number of revolutions. First, you need to understand that the distance traveled by the machine is directly related to how many times the drive sheave revolves. Specifically, each complete revolution of the sheave covers a distance equal to its circumference. In this scenario, the drive sheave has a circumference of 6 feet. If the machine needs to move at a speed of 800 feet per minute, you can calculate the number of revolutions required per minute by dividing the desired speed by the circumference of the sheave: 1. Calculate the number of revolutions per minute (RPM): - RPM = Speed (fpm) / Circumference (feet) - RPM = 800 fpm / 6 feet 2. Performing the division: - RPM = 800 / 6 ≈ 133.33 This result indicates that approximately 133.33 revolutions per minute are required to achieve a speed of 800 feet per minute when the circumference of the drive sheave