The nose is an intricate system for protecting air moving into and out of your l

Question

The nose is an intricate system for protecting air moving into and out of your lungs which in normal breathing involves moving about 100 mL of air per second. The nasal passages have a cross section of 0.5cm^2 which is considerably narrower than your throat, which is typically 6.3 cm^2 in cross section. Outside air can contain bacteria or other harmful contaminants and so a highly viscous secretion known as mucus is designed to trap foreign particles that enter the nose through breathing. The mucus viscosity is about 22 Pa-s, which is about 400,000 times that of water. Around the nasal channel are sinus cavities, which are sacs that can drain mucus into the nasal passages. (Note that air does not go through the sinuses; it does go through the nasal channel and passages.) The reaction of the body to a perceived attack is to produce more mucus as a defense, which leads to congestion and blowing your nose. Two situations arise. When your nose is clogged, the goal is to remove the blockage. On the other hand, when you just have more than normal mucus, but air can flow through your nose, the goal is to help empty your sinuses. (Note that for the purpose of this problem, which does not involve much change in absolute pressure, you can assume air is incompressible, with constant density of 1.29 kg.m^3)

1. If you breath out through your mouth: (A) air has the same velocity whichever way it goes, (B) the air has a higher velocity than if it goes out your nose, (C) the air has a lower velocity that if it goes out your nose.

2. If you double the velocity of air going through the nasal passages, the pressure in the sinuses (A) goes up four times, (B) stays the same, (C) goes down four times

3. If your nose is completely clogged and you try to blow it out, you are generating pressure from your lungs. (A) the smaller your nasal passage, the less force the pressure from your lungs will exert on the clog. (B) the smaller your nasal passage the more force your pressure will exert on the clog

4. If your cold is starting to clear, blowing your nose can clear your sinuses because (A) the flow creates a low pressure and pulls the mucus out of the sinus cavities, (B) the flow creates high pressure and blows the mucus out of the sinus cavities.

PLEASE, PLEASE EXPLAIN YOUR ANSWERS!!!

Explanation / Answer

The answers are:

1. Option C : The velocity is inversely proportional to the area (v= Q/A) where A is the area of the passage and Q is discharge so the passage area of mouth is more than that of nose so the velocity of air through mouth will be less than the Nasal Cavity.

2. Option C: It goes down four times. Consider the bernoulli equation, between any two section the bernoulli equation has to be constant as per the law of conservation of energy. The velocity head is given by v2/2g so if the velocity is doubled the factor of 4 comes out and to maintain the bernoulli equation, the pressure head has to decrease which is by 4 times and hence the net change will be zero.

3. Option A : The lesser the nasal passage area the greater will be velocity (as v=Q/A) hence the velocity head will be more and the pressure head required will be less and less pressure has to be generated from lungs

4. Option A: low pressure means high velocity of clearance,

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