1. What Is Average Velocity?
Average velocity tells us the overall change in position per unit time. It depends on displacement, not distance.
It gives a simple value that describes the entire journey, even if the object’s motion was not steady.
1.1. Why We Need Average Velocity
In real life, direction and speed change many times. Instead of studying every small change, average velocity gives a clear picture of the entire motion.
2. Formula for Average Velocity
The formula for average velocity is:
\( \text{Average Velocity} = \dfrac{\text{Total Displacement}}{\text{Total Time}} \)
This shows that only the straight-line change in position matters.
2.1. Example Calculation
If you move 15 meters east in 5 seconds, then your average velocity is:
\( \dfrac{15}{5} = 3 \, \text{m/s east} \)
2.2. Units
Average velocity is measured in:
- meters per second (m/s)
- kilometers per hour (km/h)
3. Average Velocity vs Average Speed
Even though average speed and average velocity may sound similar, they are different:
- Average speed uses total distance.
- Average velocity uses total displacement.
3.1. Example Showing the Difference
If you walk 10 meters forward and 10 meters back to your starting point:
Average speed = \( \dfrac{20}{t} \) (distance = 20 m)
Average velocity = \( \dfrac{0}{t} = 0 \) (displacement = 0)
4. When Average Velocity Becomes Zero
Average velocity becomes zero when the object returns to its starting point. This is because the displacement becomes zero.
4.1. Examples
- Completing one full round of a circular track.
- Going to the market and coming back home.
- Walking back to where you started after a stroll.
5. Average Velocity When Directions Change
If an object changes its direction during motion, the total displacement may decrease even if distance increases. This affects the average velocity.
5.1. Example with Changing Directions
You walk 6 meters east, then 2 meters west.
Total displacement = \( 6 - 2 = 4 \) m east
If this takes 4 seconds, then:
Average velocity = \( \dfrac{4}{4} = 1 \, \text{m/s east} \)