Finding mass using multiple integrals

[nb89]

The density per unit area of a circular lamina of radius a varies as the cube of the distance from a single point on the edge. Find the mass of this lamina.


im guessing id have to do ρdxdydz, and maybe use polar coordinates but I am completely lost. I am used to the question giving me an equation for the density which this doesn't have.

Any help would be much appreciated
(This is an exam question i had today but failed miserably at!)

 

[tiny-tim]

The density per unit area of a circular lamina of radius a varies as the cube of the distance from a single point on the edge. Find the mass of this lamina.

im guessing id have to do ρdxdydz, and maybe use polar coordinates but I am completely lost. I am used to the question giving me an equation for the density which this doesn't have.

Hi nb89!

i] you do have an equation for the density … it's the cube of that distance

ii] in problems like this, choose suitable slices before integrating …

in this case, arcs of thickness dr