Average Speed and Velocity

Before we can learn about average speed or average velocity, it is important to understand the difference between distance and displacement.

Distance is a scalar quantity that indicates how much ground the object has covered. However, displacement on the other hand is a vector quantity. It is the shortest distance between the end and the start point.

Example: If a particle is moving in a circle, upon completion of one revolution, the distance covered will be the circle’s perimeter. The displacement would be zero.

Velocity

 Velocity can be described as a vector quantity that has both magnitude and direction. It indicates the speed at which an object moves or changes position. It is easy to determine the direction of the velocity vector. It is the same direction as the moving object. Even though the velocity of the object is decreasing and it is slowing down slightly, the direction of the object’s motion would remain the same.

Speed

Speed is a scalar quantity that has no direction.  It indicates how fast a particle is moving. If it is very high, it means that it is moving quickly.

Average Speed

The distance covered by a particular body within a particular time period divided by the said time interval gives us the average speed of that particular body.

In general, average speed formula is:

Average Speed= Total Distance/Total Time Taken

Let’s have a look at the example below to understand more clearly: 

While travelling from Bangalore to Mangalore, Rahul drove his car for 3 hours at 70 kmph and 4 hours at 80 kmph.

Solution:

We know that, Distance = Speed × Time

So, in 3 hours, distance covered = 3 × 70 = 210 km

in the next 4 hours, distance covered = 4 × 80 = 320 km

Total distance covered = 210 + 320 = 530 km

Total time = 3 + 4 = 7 hrs

Avg. Speed = Total distance covered/ Total Time Taken

Avg. Speed = 530/7 = 75.71 kmph

Rounded off to 76kmph

Average Velocity

The average velocity of a body in a certain time interval is given as the displacement of the body in that time interval divided by time. So if a particle covers a certain displacement AB in a time  t1to t2, then the average velocity of the particle is:

vav = ABt2 –   t1

In general, the  formula is:

Average Velocity = Total DisplacementTotal Time

Understand the concept of average velocity through the examples given below.