Physics for Scientists and Engineers: A Strategic Approach with Modern Physics (3rd Edition)

Published by Pearson
ISBN 10: 0321740904
ISBN 13: 978-0-32174-090-8

Chapter 20 - Traveling Waves - Exercises and Problems - Page 588: 50

Answer

The earthquake was 1200 km away.

Work Step by Step

Let $t_p$ be the time that the P-wave took to reach the seismograph. Let $t_s$ be the time that the S-wave took to reach the seismograph. Note that $t_s = t_p + 120~s$ We can use the P-wave to write an expression for the distance. $d = v_p~t_p$ $d = (8000~m/s)~t_p$ We can use the S-wave to write an expression for the distance. $d = v_s~t_s$ $d = (4500~m/s)~(t_p+120~s)$ $d = (4500~m/s)~t_p+540,000~m$ We can equate the two expressions for the distance and solve for $t_p$: $(8000~m/s)~t_p = (4500~m/s)~t_p+540,000~m$ $(3500~m/s)~t_p = 540,000~m$ $t_p = \frac{540,000~m}{3500~m/s}$ $t_p = 154.3~s$ We can use the P-wave to find the distance. $d = (8000~m/s)~t_p$ $d = (8000~m/s)~(154.3~s)$ $d = 1.2\times 10^6~m = 1200~km$ The earthquake was thus 1200 km away.
Update this answer!

You can help us out by revising, improving and updating this answer.

Update this answer

After you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.