A rod has length 3 meters and radius (1/sqrt(pi)) meters. At a distance x meters from its left end, the density of the rod is given by delta(x)= 4+5x g/m^3. Find the total mass

Question

A rod has length 3 meters and radius (1/sqrt(pi))  meters. At a distance x meters from its left end, the density of the rod is given by delta(x)= 4+5x g/m^3. Find the total mass

anonymous · Answer

We will begin by dividing the rod into into many infinitesimal segments of length dx. The mass of each segment is dm

anonymous · Answer

u understand?

anonymous · Answer

Basically I'm trying to figure out whether this is a one dimensional, 2 d or 3d

anonymous · Answer

the density varies with only x, so this is essentially 1-d

anonymous · Answer

Well it's the radius portion of it that's throwing me off

anonymous · Answer

Do you get how we divide the rod into small discs

anonymous · Answer

yeah i do. I find integral from 0 to 3 for 4+5x dx

anonymous · Answer

but that's not the right answer

anonymous · Answer

Recall that 4+5x is the DENSITY. 
dm = Density x length x Area

anonymous · Answer

integral from 0 to 3
of
(4+5x)(pi)(r^2)dx

anonymous · Answer

yeah i know but r = 1/sqrt(pi) so (1/sqrt(pi))^2 = 1/pi so 1/pi * pi = 1

anonymous · Answer

which leaves us with integral from 0 to 3 for 4+5x dx

anonymous · Answer

34.5

anonymous · Answer

yeah that's what i got, but that's not the right answer

anonymous · Answer

whts the right ans?

anonymous · Answer

i don't know haha, that's why i'm seeking help. I've been working on this one for a while and I can't figure it out

anonymous · Answer

Well...what you did seems legit to me

anonymous · Answer

yeah me too. At least that's what I thought

anonymous · Answer

what would be the units? I found 34.5 g

anonymous · Answer

yes

anonymous · Answer

haha never mind it worked this time. I guess it didn't like 69/2. Stupid program