High School Physics + more

# Difference between average speed and average velocity

Last updated on February 8th, 2024 at 11:54 am

## Average Speed

If a car travels 200 meters in 10 seconds, we say its average speed is 20 meters per second, the average speed being the distance traveled divided by the time required to cover the distance:
Average speed = distance / elapsed time……………..(1)

Equation (1) indicates that the unit for average speed is the unit for distance divided by the unit for time, or meters per second (m/s) in SI units.

Speed is a useful idea because it indicates how fast an object is moving. However, speed does not reveal anything about the direction of the motion. To describe how fast an object moves and the direction of its motion, we need the vector concept of velocity.

## Average Velocity

To define the velocity of an object, we will use two concepts that we have already encountered, displacement and time.

Suppose in the above diagram, the initial position of the car is x0 when the time is t0. After some time it arrives at the final position x at time t. The difference between these times is the time required for the car to travel between the two positions. We denote this difference by the shorthand notation ∆t (delta t).