V= s/t = 400/4.5=800/9 (km/h)
Given:
density of air at inlet, 
density of air at inlet, 
Solution:
Now,

(1)
where
A = Area of cross section
= velocity of air at inlet
= velocity of air at outlet
Now, using eqn (1), we get:

= 1.14
% increase in velocity =
=114%
which is 14% more
Therefore % increase in velocity is 14%
1. True
2. False
Does that answer your question?
To solve this exercise it is necessary to use the concepts related to Difference in Phase.
The Difference in phase is given by

Where
Horizontal distance between two points
Wavelength
From our values we have,


The horizontal distance between this two points would be given for

Therefore using the equation we have




Therefore the correct answer is C.
The gravitational force would get stronger because the farther the two masses are separated the more gravitational force will be used to pull them together the closer they are the less gravitational pull is used to pull them together