Question

A snowball is melting as its radius, surface area and volume are all decreasing, but at different rates. Suppose it is a perfect sphere and the surface area is a quadratic function of the radius: A=4 pi r^2.

What is the exact change in the surface area when the diameter changes from 8cm to 7.8cm?


b) Calculate the differential dA and use it to approximate the change in part (a).

Answer 1

4 pi (8^2 - 7.8^2)

Answer 2

oh ok can you help me with this question...its like 4 parts

Answer 3

so for a, its what you just wrote?

Answer 4

is it right??

Answer 5

i cant verify. im looking at a hard copy of a pratice test

Answer 6

this is a free response question

Answer 7

i might be guiding you to wrong direction.

Answer 8

well i can take what you give me and go confirm with my teacher...its better than going speak to my teacher with nothing

Answer 9

find dA/dr on second and put value r = 7.8 on second

Answer 10

okay ... this is just an experiment. I am not really sure if it works or not.

Answer 11

to calculate the differential dA....i do what?

Answer 12

find dA/dr on second and put value r = 7.8 on second ... first

Answer 13

2pi 7.8^2?

Answer 14

no .. differentiate it with respect to r first

Answer 15

12pir^2??? im confuse now lol

Answer 16

4 pi (8^2 - 7.8^2) ??

Answer 17

dA/dr = 8 pi r .. i guess it is that way??

Answer 18

and put the value of R

Answer 19

the r isnt squared?

Answer 20

because it has been differentiated

Answer 21

oh yea, but how did you get the 8?

Answer 22

take derivative of A