Physics Waves SZABMU 2024
PMDC Verified Question 3 of 125
What will be the fundamental frequency in a stretched string, when its is plucked at central point while it has a speed of \( 48 \text{ ms}^{-1} \) with string length of 8m?
A
3 Hz
B
6 Hz
C
9 Hz
D
12 Hz
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option A: 3 Hz
Concept:

Plucking a string exactly at its center forces the center to become an antinode, establishing the most basic, single-loop standing wave: the fundamental mode.

Formula:

$$ f_1 = \frac{v}{2L} $$

Solution:

  • We are given the wave speed \( v = 48 \text{ m/s} \) and the string length \( L = 8 \text{ m} \).


  • Substitute these into the fundamental frequency formula:


  • \( f_1 = \frac{48}{2 \times 8} \).


  • \( f_1 = \frac{48}{16} \).


  • \( f_1 = 3 \text{ Hz} \).


Why other options are incorrect:

If a student assumes wavelength equals length (forgetting the factor of 2), they calculate 6 Hz (Option B). 12 Hz would require dividing 48 by 4.

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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