The speed of sound Medium Air (0C) Air (20°C) Helium (0°C) Ethyl alcohol Water Human tissue (ultrasound Lead Aluminum Granite Diamond
Speed (m/s) 331 343 970 1170 1480 1540 1200 5100 6000 12.000

Oil explorers set off explosives to make loud sounds, then listen for the echoes from underground oil deposits. Geologists suspect that there is oil under 480-m-deep Lake Physics. It's known that Lake Physics is carved out of a granite basin. Explorers detect a weak echo 0.930 ss after exploding dynamite at the lake surface. Part A If it's really oil, how deep will they have to drill into the granite to reach it

Explanation:

Let the required depth be d .

Sound will first travel trough 480 m deep lake . Then it will enter granite layer .   Sound travelling through granite will reach oil level , get reflected and come back to the surface of lake as echo . Total time taken by sound to travel total distance  is .93 s

Total distance = 2d + 2 x 480 m

= 2d + 960 m

speed of sound in granite is given as 6000 m / s and speed through water is 1480 m /s

total time taken

= 2d / 6000 + 960 / 1480 = .93

2d / 6000 + .6486 = .93

2d / 6000 = .2814

d= 844.2 m

force is mass*acceleration.

we have a very small mass: 11.4*0.001 kg

if we want 0.035n of force, we need an acceleration:

0.035 = 11.4*0.001*a

a = 0.035/(11.4*0.001) m/s^2

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