(a) Solve for v(t) if the raindrop falls from rest. (2) v(t) = (b) This model assumes that the rate at which the raindrop evaporates-that is, the rate at which it loses mass-is proportional to its surface area, with constant of proportionality k < 0. This assumption implies that the rate at which the radius r of the raindrop decreases is a constant. Show that the radius of the raindrop at time t is r(t) = (k/p)t + ro Letting A denote the surface area of the raindrop and m the mass, the model assumes that dmk-A. Since mass equals density times volume m= A = Plugging these formulas into the differential equation gives: =k-4mr²2 dk. 4m² Integrating the above differential equation gives Plugging in r(0)= re gives C= 70 r(t) and a sphere of radius r has volume (assuming r= 0) so that and surface area we obtain the following formulas for m and A in terms of p and r. (c) If ro= 0.04 ft and r= 0.006 ft 10 seconds after the raindrop falls from a cloud, determine the time at which the raindrop has evaporated completely. (Round your answer 11.8 ✔sec one decimal place.)

College Algebra
10th Edition
ISBN:9781337282291
Author:Ron Larson
Publisher:Ron Larson
Chapter3: Polynomial Functions
Section3.5: Mathematical Modeling And Variation
Problem 7ECP: The kinetic energy E of an object varies jointly with the object’s mass m and the square of the...
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(a) Solve for v(t) if the raindrop falls from rest.
9p
4r
v(t) =
(b) This model assumes that the rate at which the raindrop evaporates-that is, the rate at which it loses mass-is proportional to its surface area, with constant of proportionality k < 0. This assumption implies that the rate at which the radius r of the raindrop
decreases is a constant. Show that the radius of the raindrop at time t is r(t) = (k/p)t + ro.
Letting A denote the surface area of the raindrop and m the mass, the model assumes that
dm
dt
Since mass equals density times volume
m =
A =
= k. A.
4
3
Plugging these formulas into the differential equation gives:
[
dt
r(t) =
dr
dt
= k. 4tr²
= k. 4πr²
= k (assuming r = 0)
=
Integrating the above differential equation gives
r(t) =
+ C.
Plugging in r(0) = ro gives C = ro
and a sphere of radius r has volume
X
so that
and surface area
, we obtain the following formulas for m and A in terms of p and r.
(c) If ro = 0.04 ft and r = 0.006 ft 10 seconds after the raindrop falls from a cloud, determine the time at which the raindrop has evaporated completely. (Round your answer to one decimal place.)
11.8
sec
Transcribed Image Text:(a) Solve for v(t) if the raindrop falls from rest. 9p 4r v(t) = (b) This model assumes that the rate at which the raindrop evaporates-that is, the rate at which it loses mass-is proportional to its surface area, with constant of proportionality k < 0. This assumption implies that the rate at which the radius r of the raindrop decreases is a constant. Show that the radius of the raindrop at time t is r(t) = (k/p)t + ro. Letting A denote the surface area of the raindrop and m the mass, the model assumes that dm dt Since mass equals density times volume m = A = = k. A. 4 3 Plugging these formulas into the differential equation gives: [ dt r(t) = dr dt = k. 4tr² = k. 4πr² = k (assuming r = 0) = Integrating the above differential equation gives r(t) = + C. Plugging in r(0) = ro gives C = ro and a sphere of radius r has volume X so that and surface area , we obtain the following formulas for m and A in terms of p and r. (c) If ro = 0.04 ft and r = 0.006 ft 10 seconds after the raindrop falls from a cloud, determine the time at which the raindrop has evaporated completely. (Round your answer to one decimal place.) 11.8 sec
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