What is the rotational inertia of the pole

[mybrohshi5]

Homework Statement

A 2.75 m long pole is balanced vertically on its tip. It starts to fall and its lower end does not slip.

the mass of the pole is 12.93 kg

What is the rotational inertia of the pole about an axis through its lower end and perpendicular to the pole?

Homework Equations

I = 1/2mr²

The Attempt at a Solution

I = 1/2(12.93kg)(2.75)²

I = 48.9 kgm²

this was wrong so maybe i thought to use the center of the pole as my R since the mass in distributed throughout the pole


I = 1/2(12.93kg)(2.75/2)²

I = 12.22 kgm²

Does this look right?

thanks for any help

 

[berkeman]

Homework Statement

A 2.75 m long pole is balanced vertically on its tip. It starts to fall and its lower end does not slip.

the mass of the pole is 12.93 kg

What is the rotational inertia of the pole about an axis through its lower end and perpendicular to the pole?

Homework Equations

I = 1/2mr²

The Attempt at a Solution

I = 1/2(12.93kg)(2.75)²

I = 48.9 kgm²

this was wrong so maybe i thought to use the center of the pole as my R since the mass in distributed throughout the pole


I = 1/2(12.93kg)(2.75/2)²

I = 12.22 kgm²

Does this look right?

thanks for any help

What does the Parallel Axis Theorem say about how to do this problem?

 

[nickjer]

Does your book have a list of moment of inertias for different shapes? And any of those shapes resemble a pole?

 

[mybrohshi5]

yeah it says

I = 1/3 m L^2

thank you :) that worked perfectly