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~christina~

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## Homework Statement

Two points A and B on the surface of the Earth are at the same longitude and 60 deg apart in latitude. Suppose an earthquake at point A creates a P wave that reaches B by traveling straight throught he body of the Earth at constant speed of 7.80m/s. The earthquake also creates a Rayleigh wave that travels along the surface of the Earth at 4.50km/s.

a) which of these 2 waves arives at B first?

b) What is the time difference in the arrival of these 2 waves at B? Take the Earth's radius to be 6,370km.

## Homework Equations

well I found this online for the distance

D= R arc cos[sin(lat 1) x sin(lat 2) + cos (lat 1) x cos (lat 2) x cos [ lon 2- lon 1]]

y(x,t)= f(x- vt)

## The Attempt at a Solution

well I first calculated the distance between the 2 points with the equation I found online.

D= R arc cos[sin(lat 1) x sin(lat 2) + cos (lat 1) x cos (lat 2) x cos [ lon 2- lon 1]]

R of earth= 6,370km

lat 1 = 0

lat 2= 60 deg => [tex] \pi / 3[/tex]

lon 1= 0

lon 2= 0

D= 6,370km arc cos[sin(0) x sin([tex] \pi / 3[/tex]) + cos (0) x cos ([tex] \pi / 3[/tex]) x cos [ 0]]

D= 6,370km arc cos [0 + 0.5]

D= 6,670.64km

**x= 6,670.64km**

But as to how to find the time has me confused a bit.

I think I use this equation where I just solve for time then subtract the 2 times for the different waves but I'm not 100% certain. (that's where I need help)

**y(x,t)= f(x- vt)**

for the 1st wave

y(6,670,640m,t)= f(6,670,640m - 7,800m/s (t))

same for the Raleigh wave

y(6,670,640m,t)= f(6,670,640m - 4,500km/s (t))

**Or do I just use V= d/t and solve for t??**

can someone help me out with which equation to use to find the time it takes for a wave to reach a certain distance?

can someone help me out with which equation to use to find the time it takes for a wave to reach a certain distance?

Thanks

Well I'm not sure how to solve for t since isn't y the transverse position of the wave which I just don't have in the information?

Thanks a lot

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