To differentiate between average speed and average velocity, it's essential to understand the definitions and characteristics of both terms. The correct answer to your question is option b: "Average speed is total distance travelled per unit time while average velocity is total displacement per unit time." Let's break this down further to clarify these concepts.
Understanding Average Speed
Average speed is a scalar quantity, which means it only has magnitude and no direction. It is calculated by taking the total distance traveled and dividing it by the total time taken. The formula can be expressed as:
- Average Speed = Total Distance / Total Time
For example, if a car travels 150 kilometers in 3 hours, the average speed would be:
- Average Speed = 150 km / 3 h = 50 km/h
Diving into Average Velocity
In contrast, average velocity is a vector quantity, meaning it has both magnitude and direction. It is defined as the total displacement (the shortest straight-line distance from the initial to the final position) divided by the total time taken. The formula for average velocity is:
- Average Velocity = Total Displacement / Total Time
For instance, if the same car travels 150 kilometers east in 3 hours, the average velocity would be:
- Average Velocity = 150 km east / 3 h = 50 km/h east
Key Differences
Here are the main distinctions between average speed and average velocity:
- Nature: Average speed is scalar; average velocity is vector.
- Calculation: Average speed considers total distance; average velocity considers total displacement.
- Direction: Average speed does not include direction; average velocity does.
Real-World Application
Imagine a runner who completes a circular track of 400 meters in 100 seconds. The total distance traveled is 400 meters, but the displacement (the shortest distance from start to finish) is 0 meters, as they end up where they started. Here, the average speed would be:
- Average Speed = 400 m / 100 s = 4 m/s
However, the average velocity would be:
- Average Velocity = 0 m / 100 s = 0 m/s
This example illustrates how average speed can be positive while average velocity can be zero, highlighting the importance of understanding both concepts in physics.
