I have to calculate the resistance of a bar that is shaped like a fructum and I'm only given the radius of both ends, not its length.(adsbygoogle = window.adsbygoogle || []).push({});

The formula to calculate the resistance in general is

[tex]R = \rho * \frac{l}{A}[/tex]

And the formula for the volume of a fructum is

[tex]V = \frac{\pi * l}{3} (r^2_2 * r_2r_1 * r^2_1)[/tex]

My problem is that I have difficulties incorporating the formula for the volume into the formula for the resistance.

Would it be possible to calculate the volume of the fructum (which would be dependant on l) and treat it like it's a cube with the same volume? That way, I could use [tex]A = \frac{V}{l}[/tex], then divide the volume by l and enter it into the formula for R.

Other than that, I have no idea what approach to take.

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Resistance of a fructum-shaped bar

**Physics Forums | Science Articles, Homework Help, Discussion**