3. A large wooden turntable has the shape of a flat uniform disk of radius 1.8 m and a total mass of 150 kg. The turntable is initially rotating at 4.00 rad/s about a vertical axis through its center. Suddenly, a 60 kg parachutist makes a soft landing near the outer edge. (a) Find the angular speed of the turntable after the parachutist lands. (Assume you can treat the parachutist as a particle.) (b) Compute the kinetic energy before and after the parachutist lands.

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### Physics Problem: Rotational Motion of a Turntable

**Problem Statement:**

3. A large wooden turntable has the shape of a flat uniform disk of radius 1.8 m and a total mass of 150 kg. The turntable is initially rotating at 4.00 rad/s about a vertical axis through its center. Suddenly, a 60 kg parachutist makes a soft landing near the outer edge.

1. **(a)** Find the angular speed of the turntable after the parachutist lands. (Assume you can treat the parachutist as a particle.)
2. **(b)** Compute the kinetic energy before and after the parachutist lands.

**Detailed Explanation:**

To solve this problem, we will use the principles of conservation of angular momentum and kinetic energy.

#### (a) Angular Speed After Landing

1. **Calculate Initial Angular Momentum (L_initial)**
   - For a disk, the moment of inertia (I) is \( I = \frac{1}{2} m r^2 \), where \( m \) is the mass and \( r \) is the radius.
   - For the turntable: \( I_{turntable} = \frac{1}{2} \times 150 \text{ kg} \times (1.8 \text{ m})^2 \)
   - Calculate \( I_{turntable} \):

     \[
     I_{turntable} = \frac{1}{2} \times 150 \times 3.24 = 243 \text{ kg} \cdot \text{m}^2
     \]

   - Initial angular momentum \( L_{initial} \) is given by \( L = I \omega \):

     \[
     L_{initial} = 243 \times 4.00 = 972 \text{ kg} \cdot \text{m}^2 \cdot \text{s}^{-1}
     \]

2. **Calculate Final Angular Momentum (L_final)**
   - After the parachutist lands, the system's moment of inertia changes. Treat the parachutist as a point mass at the edge of the disk. The moment of inertia of the parachutist is \( I_{parachutist} = m r^2 \):

     \[
     I_{parachutist} = 60 \text{ kg} \
Transcribed Image Text:--- ### Physics Problem: Rotational Motion of a Turntable **Problem Statement:** 3. A large wooden turntable has the shape of a flat uniform disk of radius 1.8 m and a total mass of 150 kg. The turntable is initially rotating at 4.00 rad/s about a vertical axis through its center. Suddenly, a 60 kg parachutist makes a soft landing near the outer edge. 1. **(a)** Find the angular speed of the turntable after the parachutist lands. (Assume you can treat the parachutist as a particle.) 2. **(b)** Compute the kinetic energy before and after the parachutist lands. **Detailed Explanation:** To solve this problem, we will use the principles of conservation of angular momentum and kinetic energy. #### (a) Angular Speed After Landing 1. **Calculate Initial Angular Momentum (L_initial)** - For a disk, the moment of inertia (I) is \( I = \frac{1}{2} m r^2 \), where \( m \) is the mass and \( r \) is the radius. - For the turntable: \( I_{turntable} = \frac{1}{2} \times 150 \text{ kg} \times (1.8 \text{ m})^2 \) - Calculate \( I_{turntable} \): \[ I_{turntable} = \frac{1}{2} \times 150 \times 3.24 = 243 \text{ kg} \cdot \text{m}^2 \] - Initial angular momentum \( L_{initial} \) is given by \( L = I \omega \): \[ L_{initial} = 243 \times 4.00 = 972 \text{ kg} \cdot \text{m}^2 \cdot \text{s}^{-1} \] 2. **Calculate Final Angular Momentum (L_final)** - After the parachutist lands, the system's moment of inertia changes. Treat the parachutist as a point mass at the edge of the disk. The moment of inertia of the parachutist is \( I_{parachutist} = m r^2 \): \[ I_{parachutist} = 60 \text{ kg} \
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