A 45.4-kg girl is standing on a 149-kg plank. Both originally at rest on a frozen lake that constitutes a frictionless, flat surface. The girl begins to walk along the plank at a constant velocity of 1.52î m/s relative to the plank. (a) What is the velocity of the plank relative to the ice surface? -0.7 Your response differs from the correct answer by more than 10%. Double check your calculations.i m/s (b) What is the girl's velocity relative to the ice surface? 1.2 Your response is within 10% of the correct value. This may be due to roundoff error, or you could have a mistake in your calculation. Carry out all intermediate results to at least four-digit accuracy to minimize roundoff error.î m/s

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**Problem Statement:**

A 45.4-kg girl is standing on a 149-kg plank. Both are originally at rest on a frozen lake that constitutes a frictionless, flat surface. The girl begins to walk along the plank at a constant velocity of 1.52 m/s relative to the plank.

**Questions:**

(a) What is the velocity of the plank relative to the ice surface?

- User's Response: 0.7 m/s ❌
- Feedback: Your response differs from the correct answer by more than 10%. Double check your calculations.

(b) What is the girl's velocity relative to the ice surface?

- User's Response: 1.2 m/s ❌
- Feedback: Your response is within 10% of the correct value. This may be due to roundoff error, or you could have a mistake in your calculation. Carry out all intermediate results to at least four-digit accuracy to minimize roundoff error.


**Explanation:**

In this problem, we are observing a classic example of the conservation of momentum on a frictionless surface. Since there are no external forces acting horizontally, the total momentum of the system (girl + plank) remains constant. 

1. When the girl walks on the plank:
   - She moves forward, exerting a force backward on the plank.
   - The plank, in turn, moves backward, equalizing the momentum exchange as they are isolated on the frictionless surface.

The calculations for such a problem typically involve using the formulas for center of mass and conservation of momentum:

- Let \( v_g \) be the girl’s velocity relative to the ice, and \( v_p \) be the plank's velocity relative to the ice.
  
The conservation of momentum equation is:

\[ (m_{\text{girl}} \cdot v_g) + (m_{\text{plank}} \cdot v_p) = 0 \]

Where:
- \( m_{\text{girl}} = 45.4 \, \text{kg} \)
- \( m_{\text{plank}} = 149 \, \text{kg} \)

Substitute: 
\[ (45.4 \cdot (1.52 + v_p)) + (149 \cdot v_p) = 0 \]
Transcribed Image Text:**Problem Statement:** A 45.4-kg girl is standing on a 149-kg plank. Both are originally at rest on a frozen lake that constitutes a frictionless, flat surface. The girl begins to walk along the plank at a constant velocity of 1.52 m/s relative to the plank. **Questions:** (a) What is the velocity of the plank relative to the ice surface? - User's Response: 0.7 m/s ❌ - Feedback: Your response differs from the correct answer by more than 10%. Double check your calculations. (b) What is the girl's velocity relative to the ice surface? - User's Response: 1.2 m/s ❌ - Feedback: Your response is within 10% of the correct value. This may be due to roundoff error, or you could have a mistake in your calculation. Carry out all intermediate results to at least four-digit accuracy to minimize roundoff error. **Explanation:** In this problem, we are observing a classic example of the conservation of momentum on a frictionless surface. Since there are no external forces acting horizontally, the total momentum of the system (girl + plank) remains constant. 1. When the girl walks on the plank: - She moves forward, exerting a force backward on the plank. - The plank, in turn, moves backward, equalizing the momentum exchange as they are isolated on the frictionless surface. The calculations for such a problem typically involve using the formulas for center of mass and conservation of momentum: - Let \( v_g \) be the girl’s velocity relative to the ice, and \( v_p \) be the plank's velocity relative to the ice. The conservation of momentum equation is: \[ (m_{\text{girl}} \cdot v_g) + (m_{\text{plank}} \cdot v_p) = 0 \] Where: - \( m_{\text{girl}} = 45.4 \, \text{kg} \) - \( m_{\text{plank}} = 149 \, \text{kg} \) Substitute: \[ (45.4 \cdot (1.52 + v_p)) + (149 \cdot v_p) = 0 \]
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