Answer:
decibels (dB)
Explanation:
The sound intensity level is a quantity derived from the sound intensity.
The intensity of a wave is defined as the power of the source of the wave divided by the area through which the power of the wave is spread, mathematically:
where
P is the power of the source
is the surface area over which the wave spreads (assuming that the wave propagates in all directions, it corresponds to the surface area of a sphere of radius 
, where r is the distance between the source of the wave and the observer)
For sound waves, the intensity is often expressed using another unit, called decibel (dB), defined as follows:
where
is the sound intensity level in decibels
I is the intensity of the sound wave
is the threshold intensity of a sound that a person can normally hear.
Let us assume the upstream rowing rate of Alicia = x
Let us assume the downstream rowing rate of Alicia = y
We already know that
Travelling time = Distance traveled/rowing rate
Then
6/(x + 3) = 4/x
6x = 4x + 12
6x - 4x = 12
2x = 12
x = 6
Then
Rowing rate of Alicia going upstream = 6 miles per hour
Rowing rate of Alicia going downstream = 9 miles per hour.
To develop this problem it is necessary to apply the concepts related to Gravitational Potential Energy.
Gravitational potential energy can be defined as
As M=m, then
Where,
m = Mass
G =Gravitational Universal Constant
R = Distance /Radius
PART A) As half its initial value is u'=2u, then
Therefore replacing we have that,
Re-arrange to find v,
Therefore the velocity when the separation has decreased to one-half its initial value is 816m/s
PART B) With a final separation distance of 2r, we have that
Therefore
Therefore the velocity when they are about to collide is 
Answer:
no where is the main part of the question dude
