Distance and Displacement

Distance -The actual path or length travelled by the object travelled by the object is called the distance.

It is a scalar quantity.

It is always positive.

It can never be zero or negative.

Displacement – It is the shortest path between initial and final point.

It is a vector quantity.

It can be positive or negative.

It can be zero.

Difference bw distance and displacement

Example 1: A body travels in a semicircular path of radius 10 m starting its motion from point ‘A’ to point ‘B’. Calculate the distance and displacement.

Example 2: A body travels 4 km towards North then he turn to his right and travels another 4 km before coming to rest. Calculate (i) total distance travelled, (ii) total displacement.

Velocity - It is defined as the displacement of the body per unit time.

Velocity = displacement travelled / time taken

SI unit = m/s (meter/second)

Average Velocity - The average velocity of a body is the total displacement travelled by the total time taken to cover this distance.

Average velocity= Total Displacement/Total Time taken

Avg. Velocity (vavg) = (Initial velocity + Final velocity)/2 = (u+v)/2

where, u = initial velocity, v = final velocity 

Example 1: During first half of a journey by a body it travel with a speed of 40 km/hr and in the next half it travels with a speed of 20 km/hr. Calculate the average speed of the whole journey.

Example 2 : If Ananya was able to travel 6 km in North in 2 hour in his car. What was her velocity?

Example 3: A car travels 20 km in first hour, 40 km in second hour and 30 km in third hour. Calculate the average speed of the train.