The answer is
C. periodic fluctuations in the intensity if sound waves.
P.E = mgh
This is the formula for potential energy.
This is where m is mass, g is the acceleration due to gravity, and h is height.
All you have to do is multiply all these numbers together.
The energy carried by a single photon of frequency f is given by:

where

is the Planck constant. In our problem, the frequency of the photon is

, and by using these numbers we can find the energy of the photon:
Answer: Physical changes in nature could then be erosion in a mountain, the melting of snow, and a river freezing over from the cold. Since none of these changes affect the chemical composition of the mountain, the snow, or the river, they are physical changes.
Explanation:
Answer:
sum of all forces on the air plane must be ZERO
So both forces must be of same magnitude
Explanation:
As we know that airplane is moving with uniform speed is horizontal plane is a straight line
so the motion of the air plane is uniform without any acceleration
So we will have

acceleration must be zero
now by Newton's law


so sum of all forces on the air plane must be ZERO