Which of the following machines is used only to change the direction of input force?

Options

A. Inclined plane
B. Single-fixed pulley
C. Scissors
D. Screw jack

Explanation

To solve the question "Which of the following machines is used only to change the direction of input force?", we will analyze each option provided.

### Step-by-Step Solution:

1. **Identify the Machines**: The options given are:
- Inclined plane
- Single fixed pulley
- Scissors
- Screw jack

2. **Understand the Function of Each Machine**:
- **Inclined Plane**: This machine is used to reduce the effort needed to lift an object by allowing it to be raised over a distance rather than straight up. It does not solely change the direction of force.
- **Single Fixed Pulley**: This machine allows you to change the direction of the force applied. When you pull down on the rope, the load moves up. This is a key characteristic of a single fixed pulley.
- **Scissors**: Scissors are used to cut objects and involve both the application of force and the direction of force, but they do not solely change the direction of the input force.
- **Screw Jack**: A screw jack is used to lift heavy loads by converting rotational motion into linear motion. It does not only change the direction of force.

3. **Determine the Correct Answer**: From the analysis, the only machine that is used solely to change the direction of the input force is the **Single Fixed Pulley**.

4. **Conclusion**: Therefore, the correct answer to the question is the **Single Fixed Pulley**.

### Final Answer:
The machine that is used only to change the direction of input force is the **Single Fixed Pulley**.

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