 #1
Alexyboy
1. 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.
2. 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]
3. 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].
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.
2. 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]
3. 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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