 #1
Alexyboy
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].
Attachments

21.3 KB Views: 252
Last edited by a moderator: