Physics Rotational & Circular Motion DUHS 2022
PMDC Verified Question 65 of 95
The angular momentum of a particle changes from 0 to \( 720 \text{ J s} \) in \( 4 \text{ s} \). The magnitude of torque is:
A
\( 2880 \text{ N-m} \)
B
\( 180 \text{ N-m} \)
C
\( 360 \text{ N-m} \)
D
\( 1440 \text{ N-m} \)
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option B: \( 180 \text{ N-m} \)
Concept:

Torque is the rotational equivalent of force. Just as Force is the rate of change of linear momentum, Torque is the rate of change of angular momentum.

Formula:

$$ \tau = \frac{\Delta L}{\Delta t} $$

Solution:

  • Find the change in angular momentum: \( \Delta L = 720 - 0 = 720 \text{ J s} \).
  • Find the time interval: \( \Delta t = 4 \text{ s} \).
  • Divide them: \( \tau = \frac{720}{4} = 180 \text{ N}\cdot\text{m} \).


Why other options are incorrect:

  • Option A incorrectly multiplies 720 and 4.
  • Option C divides by 2 instead of 4.
  • Option D multiplies 720 and 2.

Quality & Fidelity Assurance: Every question on BeambePrep is rigorously curated against the official PMDC syllabus with zero filler, zero out-of-syllabus content, and zero typos. When an authentic past paper originally contained a historical mistake or ambiguity from the examining board (such as UHS or NUMS), BeambePrep faithfully reflects the original paper while detailing the nuance and scientific consensus in the autopsy above.

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