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A horizontal vinyl record of mass 0.123 kg and radius 0.0958 m rotates freely about a vertical axis through its center with an angular speed of 4.82 rad/s and a rotational inertia of 2.19 x 10-4 kg·m2. Putty of mass 0.0400 kg drops vertically onto the record from above and sticks to the edge of the record.What is the angular speed of the record immediately afterwards?

Respuesta :

Answer:

The angular speed of the record is 1.8 [tex]\frac{rad}{s}[/tex]

Explanation:

Given:

Mass [tex]m = 0.123[/tex] kg

Radius [tex]r = 0.0958[/tex] m

Angular speed [tex]\omega _{i} = 4.82 \frac{rad}{s}[/tex]

Moment of inertia [tex]I = 2.19 \times 10^{-4 }[/tex] [tex]Kg. m^{2}[/tex]

Mass of putty [tex]M = 0.0400[/tex] Kg

For finding the final angular speed,

According to the conservation of angular momentum,

   [tex]L_{i} = L_{f}[/tex]

[tex](I \omega _{i} ) = (I + Mr^{2} ) \omega _{f}[/tex]

  [tex]\omega _{f} = \frac{I \omega _{i} }{I + Mr^{2} }[/tex]

  [tex]\omega _{f} = \frac{2.19 \times 10^{-4} \times 4.82 }{2.19 \times 10^{-4} + 0.040 \times (0.0958) ^{2} }[/tex]

  [tex]\omega _{f} = 1.8 \frac{rad}{s}[/tex]

Therefore, the angular speed of the record is 1.8 [tex]\frac{rad}{s}[/tex]