Rotating Rigid Body Homework: Find Angular Velocity

[Faefnir]

Homework Statement

Two masses of 2 kg are attached to the extremities of a 5 cm long, negligible mass and thin bar, free to rotate around a horizontal axis passing through its center. A drop of wax falls on one of the two masses at $v = 3 \frac{m}{s}$ and sticks to it. Retrieve the angular velocity of the system immediately after the impact

Homework Equations

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Angular moment:
$$ L = I \cdot \omega $$
$$ L = rp = rmv $$
Inertia moment:
$$ I = (M + M + m) \cdot r^2 $$

The Attempt at a Solution

I don't know if the wax drop mass was deliberately omitted in the text, but if so, how can I get it? Without that I can not get $\omega$. I know I should do some attempt, but the only thing that comes to mind is the inertia moment for a thin bar

$$ I_{MC} = \frac{1}{12} m \cdot l^{2} $$

Can you help me? Thanks in advance

 

[Doc Al]

I don't know if the wax drop mass was deliberately omitted in the text, but if so, how can I get it?

You'll need the mass of the wax drop to solve this. Where did you get the problem?

 

[Faefnir]

An italian homework book. Indeed the latest edition dates back to 2003

 

[Doc Al]

Oh well. Without the mass the best you can do is solve things in terms of 'm', but that's clearly not the intention since quantities are given for everything else.

 

[Faefnir]

Thank you! You have confirmed that I understand the subject well :D