If both waves have the same wavelength, then the amplitude of
their sum could be anything between 1 cm and 9 cm, depending
on the phase angle between them.
If the waves have different wavelengths, then the resultant is a beat
with an amplitude of 9 cm.
Explanation:
It is known that relation between pressure and density is as follows.
P =
where, P = pressure
= density
g = acceleration due to gravity
h = height
Putting the given values into the above formula as follows.
P =
= 
= 110495000 Pa
Now, relation between pressure and force is as follows.
P =
or, F = PA
F =
= 
Thus, we can conclude that a force of
can be experienced at such depth.
To solve this problem we will apply the concepts related to the Doppler effect. The Doppler effect is the change in the perceived frequency of any wave movement when the emitter, or focus of waves, and the receiver, or observer, move relative to each other. Mathematically it can be described as,

Here,
= Frequency of Source
= Speed of sound
f = Frequency heard before slowing down
f' = Frequency heard after slowing down
v = Speed of the train before slowing down
So if the speed of the train after slowing down will be v/2, we can do a system equation of 2x2 at the two moments, then,
The first equation is,



Now the second expression will be,



Dividing the two expression we have,

Solving for v, we have,

Therefore the speed of the train before and after slowing down is 22.12m/s
Answer : The final volume of the balloon at this temperature and pressure is, 17582.4 L
Solution :
Using combined gas equation is,
where,
= initial pressure of gas = 1 atm
= final pressure of gas = 0.3 atm
= initial volume of gas = 6000 L
= final volume of gas = ?
= initial temperature of gas = 273 K
= final temperature of gas = 240 K
Now put all the given values in the above equation, we get the final pressure of gas.

Therefore, the final volume of the balloon at this temperature and pressure is, 17582.4 L