A bungee jumper has reached a point in her
exciting plunge where the taut cord is 100 feet
long with a 1/2-inch radius and is stretching. She
is still 80 feet above the ground and is now fall-
ing at 40 feet per second. You are observing her
jump from a spot on the ground 60 feet from the
potential point of impact, as shown in the dia-
gram above.
(a) Assuming the cord to be a cylinder with
volume remaining constant as the cord
stretches, at what rate is its radius changing
when the radius is 1/2 inch?