Question

Two metal rulers of lengths 30 cm and 60 cm are kept in such a manner that a 30 cm ruler extends about 15 cm over the edge of a table and a 60 cm ruler extends about 30 cm over the edge of same table. Both the free ends are flicked.
Which of the following statements are correct regarding this?
(i) The metal ruler of length 30 cm is able to vibrate slower.
(ii) The metal ruler of length 30 cm produces a high pitch sound.
(iii) The metal ruler of length 60 cm is able to vibrate faster.
(iv) The metal ruler of length 60 cm produces a low pitch sound.

Answer 1

If the length of a vibrating body increases, the frequency of vibration decreases.
If the length of a vibrating body decreases, the frequency of vibration increases.
As the length of 30 cm scale is smaller than that of 60 cm, the 30 cm ruler will vibrate faster and the frequency of vibration will be more as compared to another ruler. Hence, the pitch of the sound produced is high.
Therefore, only statements-ii and iv are correct.