I NEED HELP THANKS! I. A person at point B observes a firecracker explode at poi

Question

I NEED HELP THANKS!

I. A person at point B observes a firecracker explode at point A. The distance hetween points A and B is 4000 yards. The sound travels at 343m/s while the light travels 3x10'm/s. Casculate how long after seeing the light from the explosion, that the person hears the sound from the explosion. ( 1 yard-3 n, i m-3.281 m Two trains A and B are traveling in opposite directions on the same track. Train A is traveling 50mi/hr and train B is traveling 80mi/hr. When they are one mile apart, both engineers apply brakes. They each decelerate at 200mi/hr. Do they crash into each other? If so, how fast are they each going when they crash? If not, how far apart are they when they come to rest? 2.

Explanation / Answer

here ,

the distance between the point A and B , d = 4000 yards

1 yard = 0.9144 meter

then

d = 3657.6 m

speed of light , c = 3*10^8 m/s

speed of sound , v = 343 m/s

let the time taken by light and sound be tl and ts

tl = distance / speed of light

tl = 3657.6 / 3*10^8

tl = 1.219 *10^-5 s

tc = distance / speed of sound

tc = 3657.6 / 343

tc = 10.66 s

after seeing the exlposion ,let the person hears the sound after t s

t = tc -tl

t = 10.66 - 1.219 *10^-5

t = 10.66 s

after seeing the exlposion , the person hears the sound after 10.66 s

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