1. Tardigrade
  2. Question
  3. Physics
  4. Earthquakes generate sound waves inside the earth. Unlike a gas, the earth can experience both transverse ( S ) and longitudinal ( P ) sound waves. Typically the speed of S wave is about 4 kms -1, and that of P wave is 8 kms -1 A seismograph records P and S waves from an earthquake. The first P wave arrives 4 mins before the first S wave. Assuming the waves travel in straight line, the distance at which the earthquake occurs is

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Q. Earthquakes generate sound waves inside the earth. Unlike a gas, the earth can experience both transverse ( $S$ ) and longitudinal ( $P$ ) sound waves. Typically the speed of $S$ wave is about $4 kms ^{-1},$ and that of $P$ wave is $8 kms ^{-1}$ A seismograph records $P$ and $S$ waves from an earthquake. The first $P$ wave arrives 4 mins before the first $S$ wave. Assuming the waves travel in straight line, the distance at which the earthquake occurs is

Waves

Solution:

$\Delta\left(\frac{\text { distance }}{\text { speed }}\right)=\Delta($ time $)$
$\left(\frac{d}{4000}\right)-\left(\frac{d}{8000}\right)=(4 \times 60) s$
$\Rightarrow \frac{d}{4}-\frac{d}{8}=2.4 \times 10^{5}$
$d=8 \times 2.4 \times 10^{5} m =1920\, km$