Suppose the rotational kinetic energy of a solid disk is 1000 J when the disk has an angular velocity of 3 rad/s. What is the disk's moment of inertia? If the mass of the disk is 50 kg, what must be its radius? moment of inertia: A. 276.5 kg-m² D. 238.5 kg-m? В. 222.2 kg-m? E. 239.2 kg-m? С. 175.9 kg-m? F. 170.3 kg-m² |--/ radius: А. 2.490 m D. 2.536 m В. 2.981 m Е. 3.341 m С. 3.212 m F. 3.195 m

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**Rotational Kinetic Energy and Moment of Inertia of a Solid Disk**

Consider a solid disk with a rotational kinetic energy of 1000 J when it has an angular velocity of 3 rad/s. We need to find the disk's moment of inertia. Further, with a disk mass of 50 kg, we will determine the disk's radius.

**Moment of Inertia Options:**

A. 276.5 kg·m²  
B. 222.2 kg·m²  
C. 175.9 kg·m²  
D. 238.5 kg·m²  
E. 239.2 kg·m²  
F. 170.3 kg·m²  

**Radius Options:**

A. 2.490 m  
B. 2.981 m  
C. 3.212 m  
D. 2.536 m  
E. 3.341 m  
F. 3.195 m  

To find the moment of inertia (\(I\)), we use the formula for rotational kinetic energy (\(K\)):

\[ K = \frac{1}{2} I \omega^2 \]

Solving for \(I\):

\[ I = \frac{2K}{\omega^2} \]

Substituting \(K = 1000\) J and \(\omega = 3\) rad/s:

\[ I = \frac{2 \times 1000}{3^2} = \frac{2000}{9} \approx 222.2 \, \text{kg·m}^2 \]

The correct choice for the moment of inertia is B. 222.2 kg·m².

For the radius (\(r\)) of the disk, use the formula for the moment of inertia of a solid disk:

\[ I = \frac{1}{2} m r^2 \]

Solving for \(r\):

\[ r = \sqrt{\frac{2I}{m}} \]

Substituting \(I = 222.2\) kg·m² and \(m = 50\) kg:

\[ r = \sqrt{\frac{2 \times 222.2}{50}} \approx 2.981 \, \text{m} \]

The correct choice for the radius is B. 2.981 m.
Transcribed Image Text:**Rotational Kinetic Energy and Moment of Inertia of a Solid Disk** Consider a solid disk with a rotational kinetic energy of 1000 J when it has an angular velocity of 3 rad/s. We need to find the disk's moment of inertia. Further, with a disk mass of 50 kg, we will determine the disk's radius. **Moment of Inertia Options:** A. 276.5 kg·m² B. 222.2 kg·m² C. 175.9 kg·m² D. 238.5 kg·m² E. 239.2 kg·m² F. 170.3 kg·m² **Radius Options:** A. 2.490 m B. 2.981 m C. 3.212 m D. 2.536 m E. 3.341 m F. 3.195 m To find the moment of inertia (\(I\)), we use the formula for rotational kinetic energy (\(K\)): \[ K = \frac{1}{2} I \omega^2 \] Solving for \(I\): \[ I = \frac{2K}{\omega^2} \] Substituting \(K = 1000\) J and \(\omega = 3\) rad/s: \[ I = \frac{2 \times 1000}{3^2} = \frac{2000}{9} \approx 222.2 \, \text{kg·m}^2 \] The correct choice for the moment of inertia is B. 222.2 kg·m². For the radius (\(r\)) of the disk, use the formula for the moment of inertia of a solid disk: \[ I = \frac{1}{2} m r^2 \] Solving for \(r\): \[ r = \sqrt{\frac{2I}{m}} \] Substituting \(I = 222.2\) kg·m² and \(m = 50\) kg: \[ r = \sqrt{\frac{2 \times 222.2}{50}} \approx 2.981 \, \text{m} \] The correct choice for the radius is B. 2.981 m.
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