Answer
$\therefore$ a) On climbing up the hill the eardrum will pop outside in the direction.
$\therefore$ b) On climbing down the hill the eardrum will pop inside in the direction.
Work Step by Step
Since the Air pressure inside the body is equal to the surface atmospheric pressure.
a) We know that when we climb up on the hill, the outside atmospheric pressure decreases with an increase in height.
On climbing up the hill the eardrum will pop outside in direction.
b) Also, when we climb down the hill, outside pressure gradually increases and becomes equal to surface atmospheric pressure.
On climbing down the hill the eardrum will pop inside in direction.
