A deep well

Classical Mechanics Level 2

Jack dropped a stone into a 78.4 m 78.4 ~\text{m} long well. After 4.23 s , 4.23~ \text{s}, he heard it hit in the water.

Determine the speed of sound in air.

Details and assumptions:

  • g = 9.8 ms − 2 g = 9.8 ~ \text{ms}^{-2}

  • Give your answer to two decimal places.

Inspiration


The answer is 340.86.

Munem Shahriar by Munem Shahriar , 18, Bangladesh

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1 solution

Munem Shahriar
Nov 18, 2017

t 1 = 2 × 78.4 9.8 = 4 t_1 = \sqrt{\dfrac{2 \times 78.4}{9.8}} = 4

t 2 = 4.23 − 4 = 0.23 s t_2 = 4.23 - 4 = 0.23 s

Hence,

v = 78.4 0.23 = 340.86 m / s v = \dfrac{78.4}{0.23} = \boxed{340.86} m/s

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