Assignment:
When a foreign object gets stuck in your windpipe you cough. The radius of your windpipe contracts so as to increase the air velocity and dislodge the obstruction. It can be shown that air velocity is related to windpipe radius by v(r) = (r0 - r)r^2 ,where r0 is the usual 'rest radius' of the windpipe. Physical constraints prevent the windpipe contracting below half its normal radius. Sketch the function v(r) and determine the optimal coughing radius.
Provide complete and step by step solution for the question and show calculations and use formulas.