ReasoningModerate2 marks
7(iii)
The diagrams given below show two sound boxes A and B with wires of same length (l) and tension (10 kgf) but different cross-sectional areas. Simultaneously, vibrating tuning forks of frequency 300 Hz are placed on the boxes A and B. The paper rider falls off in case of B but not in case of A.
The wire A resonates with a tuning fork of frequency ‘f’. Is ‘f’ greater than, less than or equal to 300 Hz? Justify your answer.
Topic: Natural frequency of a stretched string
Question wording verified against source paper
Answer
Exam answer
f is less than 300 Hz.
Explanation
Wire A is thicker, so it has greater mass per unit length. For the same length and tension, its natural frequency is lower.
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