During earthquake at one place transverse wave (S) and longitudinal wave (P) are found to be moving towards seismograph with velocities 4.5 km/s and 8.0 km/s respectively. If first P wave is detected by seismograph earlier than S wave by 4 min then epicenter of earthquake must be located approximately at ...... distance from the seismograph.

During earthquake at one place transverse wave (S) and longitudinal wa

1.	During earthquake at one place transverse wave (S) and longitudinal wave (P) are found to be moving towards seismograph with velocities 4.5 km/s and 8.0 km/s respectively. If first P wave is detected by seismograph earlier than S wave by 4 min then epicenter of earthquake must be located approximately at ...... distance from the seismograph.
Answer» 25 km 250 km 2500 km 5000 km Solution :Here `v _(S) = 4.5 km//s` `v_(p) = 8 km//s` If `t _(S) and t _(p)` are time taken by S and P WAVE RESPECTIVELY to reach seismograph, then ar per the statement `t _(S) - t _(P) = 4 min = 240 s ` Now, `d = v _(P) t _(P) = 8 t _(P) ""...(1)` Also `d =v _(S) t _(S) = 4.5 (t _(P) + 240) ""...(2)` From `(1) and (2) 8t_(P) = 4.5 t _(P) + 1080` `therefore 3.5 t _(P) = 1080 ""...(3)` `therefore t _(P) = 308 . 6s ` From (1) and (3), `d = 8 xx 308.6` `therefore d = 2468.8 km` `therefore d ~~2500km`