ABSA 4th Class Power Engineer Certificate of Competency Part A Practice Test 2026 - Free Power Engineer Practice Questions and Study Guide

To determine the linear speed of a point on the rim of a pulley, you can use the formula that relates rotational speed and linear speed. The linear speed \( v \) can be calculated as:

\[

v = r \cdot \omega

\]

where \( r \) is the radius of the pulley and \( \omega \) is the angular velocity in radians per second.

First, convert the pulley diameter to radius. With a 50 cm diameter, the radius \( r \) is:

\[

r = \frac{50 \text{ cm}}{2} = 25 \text{ cm} = 0.25 \text{ m}

\]

Next, convert the rotational speed from revolutions per minute (r/min) to radians per second. Since one revolution is \( 2\pi \) radians and there are 60 seconds in a minute, the conversion is:

\[

\omega = 960 \text{ r/min} \cdot \frac{2\pi \text{ rad}}{1 \text{ revolution}} \cdot \frac{1 \text{ min}}{60 \text{ s}}

\]

Calculating that gives:

\[