What is the Correct Radius of a Brass Rod Given Its Mass and Density?

[7starmantis]

[SOLVED] Radius Problem

A brass rod (density = 8470 kg/m3) is 12cm long and weighs 20N. What is the radius of the rod?
I'm confused when finding area. I don't think I'm using the right variables.
volume = mass/density
v = 2.04 kg / 8470 kg/m3 = 2.4X10^-4

Area = volume/length?
A = 2.4X10^-4 / .12m = .002m
A = pi r^2
r = .03m

 

[malawi_glenn]

Area is measured in m^2

And where did you have any troubles? Just do unit analysis to make yourself sure.

 

[7starmantis]

Yeah I forgot to complete the area units, sorry.
I didn't think area = volume / length was the right equation.
If it is then I have the right answer already, right?

 

[malawi_glenn]

Yeah I forgot to complete the area units, sorry.
I didn't think area = volume / length was the right equation.
If it is then I have the right answer already, right?

ok, then I see. Yes the volume of a cylinder / rod is area x lenght.

 

[7starmantis]

Ah, then I just questioned myself for no reason. I already had the correct answer.

Correct?