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## Homework Statement

The 15kg plate shown above is able to roate on its axle which is supported on the the journal bearings at A and B. A bullet is fired into the plate providing it with an initial angular momentum of 9kgm/s. Find the angular velocity of the plate when it has rotated thropugh 180 degrees from the postion shown. Neglect the mass of the bullet.

## Homework Equations

Moment of Inertia of a Plate = [tex]\frac{1}{3} \times Mass \times width^2[/tex]

[tex]L = I \omega[/tex]

Then I'm not sure, some equations I know for rotation about a fixed axis are:

[tex]\Sigma F_{n}=m\omega^2 r_{g}[/tex]

[tex]\Sigma F_{t}=m\alpha r_{g}[/tex]

[tex]\Sigma M_{g}=I_{G}\alpha[/tex]

## The Attempt at a Solution

I calculated I as 0.1125 [tex]kgm^{2}...[/tex] ([tex]\frac{1}{3} \times 15 \times 0.15^{2}[/tex])

so using [tex] \omega= \frac{L}{I}[/tex] this gives me a [tex]\omega[/tex] of 80... however I'm not sure what the units as both 80 rad s^-1 and 80ms^-1 seem unreasonable. I am also unsure how to calulate [tex]\alpha[/tex].

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