Average Speed and Average Velocity - Definition, Formula, Example, FAQs

In studying physics, we have two concepts to deal with when it comes to motion: speed and velocity. Velocity is a term used to describe how fast an object is moving with respect to its direction. Whereas, speed only tells only about how fast an object is moving.

Let's undertsand the difference between speed and velocity with the help of an example: If someone tells you that he is driving at 60 Km/hr then he is talking about the speed. On the other hand, if someone tells you that he is driving at 60 Km/hr in the north direction then he is talking about the velocity.

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This Story also Contains

1. What is Speed?
2. What is Velocity?
3. What is Average Speed?
4. What is Average Velocity?
5. Common Mistakes and Misconnects

In this article, we will clarify the difference between speed and velocity show you how to determine both, and bring examples for better understanding.

What is Speed?

Speed is used to define how fast the object is moving with respect to time. It is a scalar quantity, which means it has no direction. Speed is calculated by dividing the total distance by the total time required to cover that distance.

$$
\text { Speed }=\frac{\text { Distance }}{\text { Time }}
$$

where,

Distance is the total path covered, and Time is the duration taken to cover that distance.

• S.I Unit of speed is meters per second (m/s).

What is Velocity?

Velocity is a vector quantity, meaning it has both a magnitude and a direction. It indicates how quickly an object is moving or changing position. The velocity vector's direction is simple to determine. It moves in the same direction as the moving object. Even if the item is slowing down and the magnitude of velocity is decreasing, the object's direction will remain the same.

$$
\text { Velocity }=\frac{\text { Displacement }}{\text { Time }}
$$

where,

Displacement is the straight-line distance from the starting point to the end point, and time is the duration taken to complete this displacement.

• S.I Unit of speed is velocity is meters per second (m/s).

Also read -

• NCERT Solutions for Class 11 Physics
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• NCERT Solutions for All Subjects

What is Average Speed?

Average speed is defined as the total distance travelled divided by the total time taken to cover that distance. It represents the overall rate of motion, without accounting for changes in speed during the journey.

The formula for average speed is:

$$
\text { Average Speed }=\frac{\text { Total Distance }}{\text { Total Time }}
$$
Let's understand the concept of average speed by a numerical problem.

Example:

Rahul rode his motorcycle from Pune to Nagpur for two hours at 60 kmph and three hours at 70 kmph. Calculate average speed

Solution:

To calculate Rahul's average speed for the entire trip, we need to find the total distance travelled and the total time taken.

- For the first part of the trip ( 2 hours at $60 \mathrm{~km} / \mathrm{h}$ ):

$
\text { Distance }_1=\text { Speed } \times \text { Time }=60 \mathrm{~km} / \mathrm{h} \times 2 \text { hours }=120 \mathrm{~km}
$

- For the second part of the trip ( 3 hours at $70 \mathrm{~km} / \mathrm{h}$ ):

$
\text { Distance }_2=\text { Speed } \times \text { Time }=70 \mathrm{~km} / \mathrm{h} \times 3 \text { hours }=210 \mathrm{~km}
$

$
\text { Total Distance }=\text { Distance }_1+\text { Distance }_2=120 \mathrm{~km}+210 \mathrm{~km}=330 \mathrm{~km}
$

$
\text { Total Time }=2 \text { hours }+3 \text { hours }=5 \text { hours }
$

$
\text { Average Speed }=\frac{\text { Total Distance }}{\text { Total Time }}=\frac{330 \mathrm{~km}}{5 \text { hours }}=66 \mathrm{~km} / \mathrm{h}
$
Answer- $
66 \text { km/h }
$

What is Average Velocity?

Average velocity is defined as the total displacement (change in position) divided by the total time taken. It is a vector quantity, meaning it has both magnitude and direction, and it indicates the overall direction and rate of motion.\

Formula used to calculate average velocity is:

$
\text { Average Velocity }=\frac{\text { Total Displacement }}{\text { Total Time }}
$

The numerical examples below will help you understand the idea of average velocity.

Example:

On the x-axis, what is the average velocity of a person moving 7 metres in 4 seconds and 18 metres in 6 seconds?

Solution:
The person moves 7 meters in the first part and 18 meters in the second part. Assuming both displacements are in the same direction along the $x$-axis, the total displacement is:

$$
\text { Total Displacement }=7 \mathrm{~m}+18 \mathrm{~m}=25 \mathrm{~m}
$$

$$
\text { Total Time }=4 \mathrm{~s}+6 \mathrm{~s}=10 \mathrm{~s}
$$

$$
\text { Average Velocity }=\frac{\text { Total Displacement }}{\text { Total Time }}=\frac{25 \mathrm{~m}}{10 \mathrm{~s}}=2.5 \mathrm{~m} / \mathrm{s}
$$
The average velocity of the person is $2.5 \mathrm{~m} / \mathrm{s}$ along the x -axis.

Related Topics,

• Acceleration
• Average Velocity
• Unit of Acceleration
• Uniformly Accelerated Motion
• Angular Acceleration

Common Mistakes and Misconnects

The average velocity does not have to be the same magnitude as the average speed. People may believe that average speed and average velocity are the same thing, but average speed is determined by distance, while average velocity is determined by displacement. If an object reverses direction throughout its travel, its average speed will be greater than the average velocity's magnitude.

Average velocity is a vector, and speed is a scalar. When the displacement is in the negative direction, the average velocity can be represented as a negative integer. The average speed has no meaning in terms of direction and can only be positive or negative.