Which one of the following is a non-conservative force ?

Options

A. Force of friction
B. Magnetic force
C. Gravitational force
D. Electrostatic force

Explanation

To determine which of the given forces is a non-conservative force, we can follow these steps:

### Step 1: Understand the Definitions
- **Conservative Force**: A force is considered conservative if the work done by the force on an object moving between two points is independent of the path taken. Examples include gravitational force, electrostatic force, and magnetic force.
- **Non-Conservative Force**: A force is non-conservative if the work done by the force depends on the path taken. The work done can vary based on the route taken between two points. An example of a non-conservative force is friction.

### Step 2: Analyze Each Force
1. **Force of Friction**: This force opposes the motion of an object and is path-dependent. The work done by friction varies based on the distance traveled and the path taken.
2. **Magnetic Force**: This is a conservative force because the work done by magnetic forces on a charged particle moving in a magnetic field is path-independent.
3. **Gravitational Force**: This is also a conservative force, as the work done by gravity depends only on the initial and final heights, not on the path taken.
4. **Electrostatic Force**: Similar to gravitational and magnetic forces, the electrostatic force is conservative since the work done only depends on the initial and final positions of the charges involved.

### Step 3: Identify the Non-Conservative Force
From the analysis, we can see that:
- The **force of friction** is the only force listed that is non-conservative.

### Conclusion
Thus, the answer to the question "Which one of the following is a non-conservative force?" is:
- **Force of Friction**