Medium level calculation of center of mass

[eileen6a]

Homework Statement

~

Homework Equations

integration

The Attempt at a Solution

for a) i use linear density and calculate the mass of circumference and integrate it bottom to top. is it riight?any other methods?
for b) i use surface density and calcuate the mass of disk and intergrate bottom to top is it right?any other methods?

also do i need to use spherical coordinate? is it exceedinly difficult to use cartisian?

 

[tiny-tim]

hi eileen!

erm … where did the question go?

 

[eileen6a]

why disappear? the file as attached thx~

 

[tiny-tim]

hi eileen!

(wouldn't it have been quicker just to type the question? )

for a) i use linear density and calculate the mass of circumference and integrate it bottom to top. is it riight?

correct in principle, but difficult to say whether you're actually doing it right without seeing the calculation

for b) i use surface density and calcuate the mass of disk and intergrate bottom to top is it right?any other methods?

if by "disk" you mean "hemispherical shell", yes

and there's no other method that uses (a)

also do i need to use spherical coordinate? is it exceedinly difficult to use cartisian?

spherical is easier, but Cartesian will also work, so long as you know your trig substitutions for the integral