Just so you know, total deafness is quite different than partial deafness.
Partial deafness can be any number of things. It can be an inability to make out the contents of high notes (notes with high frequencies and few harmonics).
Partial deafness can be the inability to hear low notes. I only know one person who suffers from that.
Your response to speech is quite different. Usually you have to have people look right at you. Lip reading is an art. Most deaf people between what they partially hear and lip reading can make out about 1/2 of what is said. Guessing usually takes care of the rest. Course you can get everything all muddled by guessing.
It does change your way of life. The TV is often turned up high enough that people living 4 houses down can list to the 6 o'clock news when you do.
Music is hard to make out. The overtones are lost.
Earphones have very tinny sound.
People are not as enjoyable as they once were.
The second major reason for the difference in gravity at differentlatitudes is that the Earth's equatorial bulge (itself also caused by centrifugalforce from rotation) causes objects at the Equator to be farther from the planet's centre than objects at the poles.
Explanation:
Let h is the height of the plane above ground. x is the horizontal distance between the ground and the airport. Let s(t) is the distance between the plane and the airport. So,
...........(1)
Given, h = 4, x = 40 and s(t) = -20 mph
Differentiate equation (1) wrt t
When x = 40, 
So, the speed of the airplane is 241.14 m/s. Hence, this is the required solution.
