Physics Rotational & Circular Motion ETEA 2023
PMDC Verified Question 36 of 95
A fly wheel rotates at constant speed of \( 600 \text{ rpm} \). The angle described by the shaft in radian in one second is:
A
\( 100\pi \)
B
\( 20\pi \)
C
\( 0 \)
D
\( 20 \)
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option B: \( 20\pi \)
Concept:

RPM measures complete revolutions in a minute. We need to convert this to angular displacement (radians) per second.

Formula:

$$ \omega = \text{RPM} \times \frac{2\pi}{60} $$

Solution:

  • Convert minutes to seconds: \( 600 \text{ rev/min} = \frac{600}{60} \text{ rev/sec} = 10 \text{ revolutions/sec} \).
  • Convert revolutions to radians: Each revolution is \( 2\pi \text{ radians} \).
  • \( 10 \text{ rev/sec} \times 2\pi = 20\pi \text{ rad/s} \).
  • In exactly 1 second, the angle covered is therefore \( 20\pi \text{ radians} \).


Why other options are incorrect:

  • Option A occurs if you divide by 6 instead of 60.
  • Option D forgets the \( \pi \) multiplier entirely.

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