An athlete participates in a race now he is moving on a circular track of radius `80` m completes half a revolution in `20` s. Its average velocity is :

Options

A. `8` m/s
B. `16` m/s
C. `10` m/s
D. `12` m/s

Explanation

To solve the problem of finding the average velocity of the athlete moving on a circular track, we can follow these steps:

### Step 1: Understand the Motion
The athlete completes half a revolution on a circular track with a radius of 80 meters in 20 seconds.

### Step 2: Identify the Initial and Final Positions
- The athlete starts at point A (the starting point) and moves to point B (the point directly opposite on the circular track after half a revolution).

### Step 3: Calculate the Displacement
- The displacement is defined as the shortest distance between the initial and final positions.
- In this case, since the athlete moves from point A to point B, the displacement is the diameter of the circle.
- The diameter \( D \) can be calculated as:
\[ D = 2 \times \text{radius} = 2 \times 80 \, \text{m} = 160 \, \text{m} \]

### Step 4: Calculate the Time Taken
- The time taken to complete half a revolution is given as 20 seconds.

### Step 5: Calculate the Average Velocity
- The formula for average velocity \( V_{avg} \) is given by:
\[ V_{avg} = \frac{\text{Displacement}}{\text{Time Taken}} \]
- Substituting the values we have:
\[ V_{avg} = \frac{160 \, \text{m}}{20 \, \text{s}} = 8 \, \text{m/s} \]

### Conclusion
The average velocity of the athlete is \( 8 \, \text{m/s} \).

---