The speedometer of an automobile measures

Options

A. instantaneous velocity
B. instantaneous speed
C. both instantaneous speed and velocity
D. average speed

Answer

To solve the question regarding what the speedometer of an automobile measures, we can break it down step by step.

### Step-by-Step Solution:

1. **Understanding Speed and Velocity**:
- Speed is a scalar quantity that refers to how fast an object is moving, regardless of its direction.
- Velocity is a vector quantity that refers to the speed of an object in a specific direction.

2. **Function of a Speedometer**:
- A speedometer is an instrument found in vehicles that measures the speed of the vehicle at a given moment.
- It does not take into account the direction of travel, which is essential for determining velocity.

3. **Instantaneous Speed vs. Average Speed**:
- Instantaneous speed is the speed of the vehicle at a specific moment in time.
- Average speed is calculated over a period of time, taking the total distance traveled divided by the total time taken.

4. **Conclusion**:
- Since the speedometer provides the speed at a particular instant and does not consider direction, it measures instantaneous speed.
- Therefore, the correct answer to the question is that the speedometer measures instantaneous speed.

### Final Answer:
The speedometer of an automobile measures **instantaneous speed**.