Ashout down a well produces an echo in 2.00 seconds. how deep is the surface of the water in the well? assume the speed of sound to be 343 m/s.

t = total time taken by sound to go down the well and then come back = 2 sec

d = depth of the well

D = total distance traveled by the sound

total distance traveled by sound is given as

total distance traveled = distance traveled going down + distance traveled going up

D = d + d

D = 2 d                                                               eq-1

v = speed of sound = 343 m/s

we know that distance traveled is given as

total distance traveled = speed of sound x total time

D = v t

using eq-1

2 d = v t

2 d = (343) (2)

dividing both side by 2

d = 343 x 2/2

d = 343 m

hence surface of water is 343 m deep

i think it because equal matrices have equal dimensions, only square matrices can be symmetric. for all indices and . every square diagonal matrix is symmetric, since all off-diagonal elements are zero. in linear algebra, a real symmetric matrix represents a self-adjoint operator over a real inner product space.

electromagnetic shielding is the practice of reducing the electromagnetic field in a space by blocking the field with barriers made of conductive or magnetic materials. shielding is typically applied to enclosures to isolate electrical devices from their surroundings, and to cables to isolate wires from the environment through which the cable runs. electromagnetic shielding that blocks radio frequency electromagnetic radiation is also known as rf shielding.

the shielding can reduce the coupling of radio waves, electromagnetic fields and electrostatic fields. a conductive enclosure used to block electrostatic fields is also known as a faraday cage. the amount of reduction depends very much upon the material used, its thickness, the size of the shielded volume and the frequency of the fields of interest and the size, shape and orientation of apertures in a shield to an incident electromagnetic

from wikipedia