Question

HELP!!! when a person coughs, the trachea(windpipe contracts, allowing air to be expelled at max velocity. it can be shown that during a cough the velocity v of airflow is given by the function v=f(r)=kx^2(R-r) where r is the radius of the trachea in cm during a cough, R is the trachea's normal radius in cm, and k is a positive constant that depends on the length of the trachea. find the radius r for which the velocity of airflow is greatest.

Answer 1

Hey ask it in other greoups

Answer 2

which group??

Answer 3

this is a maths problem.

Answer 4

science, biology,

Answer 5

oh!

Answer 6

sorry

Answer 7

i think u have to differentiate f(r) to have df(r)/dr, but i can't see what's ment by the "x" in f(r)?

Answer 8

sorry...thats "r". v=f(r)=kr^2(R-r)

Answer 9

aha, then:
v=kr^2R-kr^2r, where k, R are constants
dv/dr=2kRr-3kr^2
finding the maxima by equaling to zero
0=2kRr-3kr^2

Answer 10

any particular reason for finding the maxima??