- #1
soopo
- 225
- 0
Homework Statement
Prove parallel axis theorem (Steiner's theorem).
Homework Equations
[tex] I_{parallel axis} = I_{cm} + Mr^2 [/tex]
The Attempt at a Solution
I know Wolfram's site which seems to use http://scienceworld.wolfram.com/physics/ParallelAxisTheorem.html"
I am not sure whether the hint of my friend implies to calculate similarly.
He suggests
1. present [tex] A_{mi}, A_c,[/tex] and [tex]C_{mi} [/tex] as vectocs. A is "moment of inertia", while C is "center of mass", perhaps [tex]mR^2[/tex] -term.
2. write moment of inertia's definition as [tex]A = \Epsilon m_i \rho_i ^2[/tex]
3. write [tex] \rho_i^2 = \bar{\rho_i} * \bar{\rho_i} [/tex]
4. Put the vector [tex] \bar{l} + \bar{r_i}[/tex] into the kro at (3).
5. then calculate open
This way one term is zero, because there is a vector in that term which
length is the distance of the center of the mass from itself.
I am not sure whether my friend suggests me to use tensors in the steps (1-5).
I am unsure how the steps which he outlines proves the parallel axis theorem.
It does not seem to be a robust for me.
There seems to be also different kinds of moments of inertias so I am not sure whether the steps (1-5)
form a general result.
How would you prove the theorem in the course "Physics IA"?
Last edited by a moderator: