Final answer:
The frequency in hertz of a machine part rotating at 120 rad/s is approximately 20 Hz, calculated by dividing the angular speed by 2π.
Step-by-step explanation:
The question deals with the conversion of angular speed given in radians per second to frequency in hertz. To find the frequency in hertz, we need to know that one complete revolution is 2π radians and that frequency is the number of revolutions per second. Given that the machine part rotates at 120 rad/s, we can calculate its frequency by dividing the angular speed by 2π:
Frequency (Hz) = Angular Speed (rad/s) / (2π)
Frequency (Hz) = 120 rad/s / (2π) ≈ 19.1 Hz
So the closest answer to the frequency in hertz would be 20 Hz, which is option a).