A ladder of weight 390 N and 6 m long
is placed against a vertical wall at an
angle of 300 as shown in figure. The
coefficient of friction between the
ladder and the wall is 0.25 and that
between ladder and floor is 0.38. Find
how high a man of weight 1170 N can
ascend, before the ladder begins to
slip.


To solve this problem, we will analyze the forces and torques acting on the ladder and apply the conditions of static equilibrium.

### Assumptions:
1. The ladder is uniform and has a length of \(6 \, \text{m}\).
2. The ladder forms an angle of \(30^\circ\) with the horizontal.
3. The weight of the ladder is \(390 \, \text{N}\), acting at its center of gravity (midpoint of the ladder).
4. The coefficient of friction between the ladder and the wall is \(0.25\), and between the ladder and the floor is \(0.38\).
5. The man has a weight of \(1170 \, \text{N}\), and he can ascend a certain distance before the ladder begins to slip.

### Steps:

1. **Identify Forces Acting on the Ladder**:
    - \(F_N\): Normal reaction force at the wall.
    - \(F_f\): Frictional force at the floor.
    - \(R_f\): Normal reaction force at the floor.
    - \(F_w\): Frictional force at the wall.
    - The weight of the ladder \(390 \, \text{N}\) acts at the center of the ladder (3 m from both ends).
    - The weight of the man \(1170 \, \text{N}\) acts at a distance \(x\) from the bottom of the ladder.

2. **Conditions for Static Equilibrium**:
    - **Translational equilibrium**: The sum of forces in both the vertical and horizontal directions must be zero.
    - **Rotational equilibrium**: The sum of torques about any point must be zero.

    Let's denote the length of the ladder as \(L = 6 \, \text{m}\) and the angle it makes with the floor as \(\theta = 30^\circ\).

3. **Vertical Force Balance**:
    \[
    R_f = 390 \, \text{N} + 1170 \, \text{N} = 1560 \, \text{N}
    \]

4. **Horizontal Force Balance**:
    The horizontal forces consist of the frictional force at the floor and the normal force at the wall:
    \[
    F_f = F_N
    \]
   
5. **Frictional Forces**:
    - At the floor: \(F_f \leq \mu_f R_f = 0.38 \times 1560 = 592.8 \, \text{N}\)
    - At the wall: \(F_w \leq \mu_w F_N = 0.25 F_N\)

6. **Torque Balance**:
    Taking torques about the point where the ladder touches the ground, we can write:
    \[
    F_N \cdot L \cdot \sin \theta = 390 \cdot \frac{L}{2} \cdot \cos \theta + 1170 \cdot x \cdot \cos \theta
    \]

    Substituting \(L = 6 \, \text{m}\), \(\theta = 30^\circ\), and solving for \(x\), the distance the man can ascend before the ladder slips:

    \[
    F_N \cdot 6 \cdot \sin 30^\circ = 390 \cdot 3 \cdot \cos 30^\circ + 1170 \cdot x \cdot \cos 30^\circ
    \]
    \[
    6F_N \cdot 0.5 = 390 \cdot 3 \cdot 0.866 + 1170 \cdot x \cdot 0.866
    \]
    \[
    3F_N = 1013.22 + 1014.42 \cdot x
    \]
    Also, from the horizontal force balance \(F_f = F_N \leq 592.8 \, \text{N}\), so \(F_N = 592.8 \, \text{N}\).

    Substituting this into the torque equation:
    \[
    3 \cdot 592.8 = 1013.22 + 1014.42 \cdot x
    \]
    \[
    1778.4 = 1013.22 + 1014.42 \cdot x
    \]
    \[
    765.18 = 1014.42 \cdot x
    \]
    \[
    x \approx 0.754 \, \text{m}
    \]

Thus, the man can ascend approximately **0.754 meters** before the ladder begins to slip.

Would you like further clarification or additional details on this process?

### Follow-up Questions:
1. What would happen if the coefficient of friction at the wall increased?
2. How would the result change if the ladder's weight increased?
3. What is the impact of increasing the angle of the ladder with the ground?
4. How does decreasing the friction coefficient at the floor affect the distance the man can climb?
5. What is the effect of moving the ladder closer to the vertical position?

### Tip:
The higher the coefficient of friction between surfaces, the more stable the ladder becomes, allowing a greater distance for the man to climb.

A ladder of weight 390 N and 6 m long is placed against a vertical wall at an angle of 30° as shown in figure. The coefficient of friction between the ladder and the wall is 0.25 and that between ladder and floor is 0.38. Find how high a man of weight 1170 N can ascend, before the ladder begins to slip.

Solve how high a man weighing 1170 N can ascend a 6-meter ladder placed at an angle of 30° before it slips. This problem covers static equilibrium, torque, and friction, and is suitable for Grade 11-12 physics students.

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