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WAEC Physics 2022 Paper

Question : 37

Total: 50

A hunter fires a gun at a point 408 m away from a cliff. If he hears an echo 2.4 s later, determine the speed of the sound wave

$340\,\mathrm{ms}^{-1}$
$380\,\mathrm{m}\,\mathrm{s}^{-1}$
$400\,\mathrm{m}\,\mathrm{s}^{-1}$
$680\,\mathrm{m}\,\mathrm{s}^{-1}$

Validate

Solution:

Concept:

An echo is heard when sound travels to the reflecting cliff and returns to the listener, so the total distance travelled is twice the distance to the cliff.

Explanation:

Distance from the hunter to the cliff is

408\,\mathrm{m}

Sound travels to the cliff and back, so total distance is:

d = 2 \times 408 = 816\,\mathrm{m}

Given time for the echo,

t = 2.4\,\mathrm{s}

Speed of sound is given by:

v = \frac{d}{t} = \frac{816}{2.4}

v = 340\,\mathrm{m\,s^{-1}}

Answer:

Speed of the sound wave is

340\,\mathrm{m\,s^{-1}}

, which matches option A.

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