The man pulls. the boy up to the tree limb C by walking backward. If he starts from rest when x = 0 and moves backward with a constant acceleration a = 0.2 m/s², determine the speed of the boy at the instant y = 4 m. Neglect the size of the limb. When x₁ = 0, YB 8 m, so that XA A and B are coincident, i.e., the rope is 16 m long. = -XA- C B Ув 8 m Ans. VB 1.41 m/s ↑

Elements Of Electromagnetics
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Author:Sadiku, Matthew N. O.
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### Problem Description:

A man pulls a boy up to the tree limb \( C \) by walking backward. He starts from rest when \( x_A = 0 \) and moves backward with a constant acceleration \( a_A = 0.2 \, \text{m/s}^2 \). You are required to determine the speed of the boy at the instant \( y_B = 4 \, \text{m} \). Neglect the size of the limb. When \( x_A = 0 \), \( y_B = 8 \, \text{m} \), indicating that points \( A \) and \( B \) are coincident and the rope is 16 meters long.

### Diagram Explanation:

- **Diagram Elements**: 
  - A man (at point \( A \)) is holding a rope.
  - A boy is seated and is being pulled upwards (at point \( B \)).
  - The rope passes over a tree limb (at point \( C \)).
  - Labels like \( x_A \) and \( y_B \) indicate horizontal and vertical displacements, respectively.

- **Diagram Annotations**:
  - \( x_A \): The horizontal displacement of the man.
  - \( y_B \): The vertical displacement of the boy, initially 8 meters.
  - The rope length is constant at 16 meters.

### Calculation:

To find the speed \( v_B \) of the boy at \( y_B = 4 \, \text{m} \):

1. **Use the length of the rope**:
   The total length of the rope is fixed at 16 meters.
   
   \[
   \sqrt{x_A^2 + y_B^2} = 16
   \]

2. **Differentiate with respect to time**:
   \[
   x_A \frac{dx_A}{dt} + y_B \frac{dy_B}{dt} = 0
   \]

3. **Use given information**:
   Given \( a_A = 0.2 \, \text{m/s}^2 \).

4. **Find speed \( v_B \)**:
   By solving the equations, the answer for the boy's speed at the given instant \( y_B = 4 \) is:
   
   \[
   v_B = 1.41 \, \text{m/s}
   \]

This solution illustrates
Transcribed Image Text:### Problem Description: A man pulls a boy up to the tree limb \( C \) by walking backward. He starts from rest when \( x_A = 0 \) and moves backward with a constant acceleration \( a_A = 0.2 \, \text{m/s}^2 \). You are required to determine the speed of the boy at the instant \( y_B = 4 \, \text{m} \). Neglect the size of the limb. When \( x_A = 0 \), \( y_B = 8 \, \text{m} \), indicating that points \( A \) and \( B \) are coincident and the rope is 16 meters long. ### Diagram Explanation: - **Diagram Elements**: - A man (at point \( A \)) is holding a rope. - A boy is seated and is being pulled upwards (at point \( B \)). - The rope passes over a tree limb (at point \( C \)). - Labels like \( x_A \) and \( y_B \) indicate horizontal and vertical displacements, respectively. - **Diagram Annotations**: - \( x_A \): The horizontal displacement of the man. - \( y_B \): The vertical displacement of the boy, initially 8 meters. - The rope length is constant at 16 meters. ### Calculation: To find the speed \( v_B \) of the boy at \( y_B = 4 \, \text{m} \): 1. **Use the length of the rope**: The total length of the rope is fixed at 16 meters. \[ \sqrt{x_A^2 + y_B^2} = 16 \] 2. **Differentiate with respect to time**: \[ x_A \frac{dx_A}{dt} + y_B \frac{dy_B}{dt} = 0 \] 3. **Use given information**: Given \( a_A = 0.2 \, \text{m/s}^2 \). 4. **Find speed \( v_B \)**: By solving the equations, the answer for the boy's speed at the given instant \( y_B = 4 \) is: \[ v_B = 1.41 \, \text{m/s} \] This solution illustrates
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