Physics Work & Energy NUMS 2024
PMDC Verified Question 13 of 108
At what angle of applied force, work done will be 50%?
A
30°
B
60°
C
90°
D
45°
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option B: 60°
Concept:

Work done depends on the cosine of the angle. 50% work means half of the maximum possible work.

Formula:

$$ W = W_{\text{max}} \cos \theta \implies W = Fd \cos \theta $$

Solution:

  • Maximum work (\( W_{\text{max}} \)) occurs at 0° (\( \cos 0 = 1 \)).


  • We want \( W = 0.5 \times W_{\text{max}} \).


  • Therefore, we need the angle where \( \cos \theta = 0.5 \).


  • \( \cos(60^{\circ}) = 0.5 \).


  • Thus, at 60°, the work done is 50% of the maximum.


Why other options are incorrect:

At 45°, it is \( \approx 70.7\% \) (\( 1/\sqrt{2} \)). At 30°, it is \( \approx 86.6\% \) (\( \sqrt{3}/2 \)). At 90°, it is 0%.

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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