The echo of a gunshot is heard 10 seconds after it is fired. If the velocity of sound is 330 m/s, the distance of the surface which reflects the sound is

Options

A. 33 m
B. 3300 m
C. 135 m
D. 1650 m

Answer

To solve the problem, we need to find the distance to the reflecting surface based on the time it takes for the echo to return and the speed of sound.

### Step-by-Step Solution:

1. **Understand the Problem**:
- We hear the echo of a gunshot after 10 seconds.
- The speed of sound is given as 330 m/s.

2. **Identify the Total Distance**:
- The sound travels to the reflecting surface and back. Therefore, the total distance traveled by the sound is twice the distance to the surface (2D).

3. **Use the Formula for Distance**:
- The formula for distance is:
\[ \text{Distance} = \text{Speed} \times \text{Time} \]
- In this case, the total distance traveled by the sound is:
\[ \text{Total Distance} = \text{Speed of Sound} \times \text{Total Time} \]

4. **Plug in the Values**:
- The speed of sound is 330 m/s and the total time is 10 seconds. Therefore:
\[ \text{Total Distance} = 330 \, \text{m/s} \times 10 \, \text{s} = 3300 \, \text{m} \]

5. **Calculate the Distance to the Surface**:
- Since the total distance is twice the distance to the surface (2D), we can set up the equation:
\[ 2D = 3300 \, \text{m} \]
- To find D, divide both sides by 2:
\[ D = \frac{3300 \, \text{m}}{2} = 1650 \, \text{m} \]

6. **Conclusion**:
- The distance to the reflecting surface is 1650 meters.

### Final Answer:
The distance of the surface which reflects the sound is **1650 meters**.

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