- #1

spsch

- 111

- 21

- Homework Statement
- With what speed does the tip of a 25-meter high tree hit the ground?

Assume the tree has a moment of inertia of a long thin rod.

- Relevant Equations
- ## mg* \frac {l}{2} = \frac {1}{6} *m*l^2 * (\frac {v^2} {l^2}) ##

Hi, I am still working on the same exams problems, the second last one is giving me a bit of a headache after I found this https://physics.stackexchange.com/q...r-an-upright-rigid-body-to-fall-to-the-ground which contradicts my solution.

Can I assume that when the tree hit's the ground all of it's potential energy is converted to rotational energy?

I was thinking this is why they mention the moment of inertia being that of a long thin rod.

So I went with:

## mg* \frac {l}{2} = \frac {1}{6} *m*l^2 * (\frac {v^2} {l^2}) ##

and got: v= ## \sqrt {3*g*l} ##

Can I assume that when the tree hit's the ground all of it's potential energy is converted to rotational energy?

I was thinking this is why they mention the moment of inertia being that of a long thin rod.

So I went with:

## mg* \frac {l}{2} = \frac {1}{6} *m*l^2 * (\frac {v^2} {l^2}) ##

and got: v= ## \sqrt {3*g*l} ##