Physics Work & Energy DUHS 2023
PMDC Verified Question 34 of 108
A body of mass 4 kg is moving a circle of radius 2m. if the body moves round a complete circle, what is the work done by the body?
A
8 J
B
0
C
16 J
D
5 J
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option B: 0
Concept:

There are two primary reasons work is zero here: displacement logic and force angle logic.

Formula:

$$ W = \vec{F} \cdot \vec{d} = Fd \cos \theta $$

Solution:

  • Reason 1: Over a complete circle, the start and end points are identical. Total displacement \( \vec{d} = 0 \). Therefore, Work = 0.


  • Reason 2: Centripetal force acts towards the center, while instantaneous motion is tangential (angle is 90°). Since \( \cos(90^{\circ}) = 0 \), continuous work done is zero at every instant.


Why other options are incorrect:

Options A, C, and D are calculated by blindly multiplying mass, radius, and other numbers given in the prompt, ignoring the vector nature of work.

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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