Ladder Torque
1. **State the problem:**
Calculate the total torque about the base of a 4-meter ladder due to a 600 N painter standing 3 meters from the bottom and the ladder's weight of 200 N.
2. **Identify forces and distances:**
- Painter's weight (force): $F_p = 600$ N
- Painter's distance from base: $d_p = 3$ m
- Ladder's weight (force): $F_l = 200$ N
- Ladder's length: $L = 4$ m
3. **Find the torque caused by each force:**
Torque $\tau = F \times r \times \sin(\theta)$, where $r$ is the perpendicular distance to the pivot.
Assuming the ladder is vertical against the wall, force acts vertically down, and distance is horizontal from the base, so $\theta = 90^\circ$ and $\sin 90^\circ = 1$.
4. **Calculate torque by painter:**
$$\tau_p = F_p \times d_p = 600 \times 3 = 1800$$ N·m
5. **Calculate torque by ladder weight:**
The ladder’s weight acts at its center (midpoint), i.e., at 2 m from the base.
$$\tau_l = F_l \times \frac{L}{2} = 200 \times 2 = 400$$ N·m
6. **Calculate total torque:**
$$\tau_{total} = \tau_p + \tau_l = 1800 + 400 = 2200$$ N·m
**Final answer:**
The total torque about the base of the ladder is $\boxed{2200}$ N·m.