A cyclist moving a car circular track of raidus 40 cm completes half a revolution in 40 s. Its average velocity is

Options

A. zero
B. `4 pi ms^(-1)`
C. `2 cm s^(-1)`
D. `8 pi m s^(-1)`

Explanation

To find the average velocity of the cyclist moving on a circular track, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Problem**:
- The cyclist is moving on a circular track with a radius of 40 cm.
- The cyclist completes half a revolution in 40 seconds.

2. **Identify the Initial and Final Positions**:
- When the cyclist completes half a revolution, they start at point A (one end of the diameter) and end at point B (the opposite end of the diameter).
- The displacement is the straight line distance from point A to point B.

3. **Calculate the Displacement**:
- The displacement for half a revolution on a circular track is equal to the diameter of the circle.
- The diameter \(D\) can be calculated using the formula:
\[ D = 2 \times \text{radius} \]
- Given the radius is 40 cm:
\[ D = 2 \times 40 \text{ cm} = 80 \text{ cm} \]

4. **Calculate the Average Velocity**:
- Average velocity (\(V_{avg}\)) is defined as the total displacement divided by the total time taken.
- The total time taken is 40 seconds.
- Therefore, we can calculate the average velocity using the formula:
\[ V_{avg} = \frac{\text{Total Displacement}}{\text{Total Time}} = \frac{80 \text{ cm}}{40 \text{ s}} = 2 \text{ cm/s} \]

5. **Final Answer**:
- The average velocity of the cyclist is \(2 \text{ cm/s}\).