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

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Homework Help Overview

The discussion revolves around determining the radius of a brass rod given its mass and density. The rod is specified to be 12 cm long and weighs 20 N, with a known density of 8470 kg/m³.

Discussion Character

  • Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • Participants discuss the relationship between volume, mass, density, and area, questioning the appropriateness of the equations used to find the radius. There is confusion regarding the calculation of area from volume and length.

Discussion Status

Some participants have acknowledged errors in unit conversion and expressed uncertainty about the equations used. There is a recognition that the volume of a cylinder relates to its area and length, but no consensus on the correctness of the final answer has been reached.

Contextual Notes

Participants are navigating through unit analysis and the application of formulas related to volume and area, indicating potential misunderstandings about the equations involved.

7starmantis
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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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