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

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To determine the radius of a brass rod with a density of 8470 kg/m3, a length of 12 cm, and a weight of 20 N, the volume is calculated using the formula volume = mass/density. The mass is derived from the weight, leading to a volume of approximately 2.4 x 10^-4 m^3. The area is then found using the relationship area = volume/length, resulting in an area of 0.002 m^2. The radius is calculated from the area using the formula A = πr^2, yielding a radius of 0.03 m. The discussion clarifies the correct application of formulas and confirms the solution.
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[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
 
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Area is measured in m^2

And where did you have any troubles? Just do unit analysis to make yourself sure.
 
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?
 
7starmantis said:
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.
 
Ah, then I just questioned myself for no reason. I already had the correct answer.

Correct?
 
Last edited:

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