Chapter 11

NCERT
Class 9
Science
Solutions
7. Two children are at opposite ends of an aluminum rod. One strikes the end of the rod with a stone. Find the ratio of times taken by the sound wave in air and in aluminum to reach the second child.

Question:

Two children are at opposite ends of an aluminum rod. One strikes the end of the rod with a stone. Find the ratio of times taken by the sound wave in air and in aluminum to reach the second child.

Answer:

Velocity of sound in air v1 = 346 ms–1

Velocity of sound in aluminum v2 = 6420 ms–1

Let the length of the aluminum pipe = x m.

∴ Time = distance/velocity

Time taken in the air =  xm / 346ms-1

Time taken in the air =  x / 346s

Time taken in aluminum = xm / 6420ms-1

Time taken in aluminum = x / 6420s

Required ratio = x / 346s ÷ x / 6420s

x/346 x 6420/x

= 18.55

Buy Latest Books

Teacher's Corner