Answer :

Of course! Let's walk through the problem step-by-step.

### Understanding the Problem
We need to calculate the effort required to lift an 800 kg load to a height of 11 feet using a single movable pulley.

### Key Concept
A movable pulley allows you to reduce the effort needed to lift a load. For a single movable pulley, the effort needed to lift the load is halved.

### Step-by-Step Solution:

1. Identify the load and other given values:
- Load: [tex]\( 800 \)[/tex] kg
- Distance: [tex]\( 11 \)[/tex] ft (although the distance is given, it is not directly needed to calculate the effort required with a pulley system).

2. Understand the effort reduction:
- For a single movable pulley, the effort required to lift the load is halved. This means that you only need half the force you would normally need to lift the load directly.

3. Apply the effort reduction to the load:
- Calculate the effort needed using the formula for a single movable pulley:
[tex]\[ \text{Effort} = \frac{\text{Load}}{2} \][/tex]
- Here, the load is [tex]\( 800 \)[/tex] kg.

4. Perform the calculation:
- Substitute the given load into the formula:
[tex]\[ \text{Effort} = \frac{800}{2} = 400 \, \text{kg} \][/tex]

### Final Answer

The effort needed to lift an 800 kg load using a single movable pulley to a height of 11 feet is [tex]\( 400 \)[/tex] kg.