A man walks on a straight road from his home to market 2.5 km away with speed of 5 km/h Finding the market closed, he instantly turns and walks back with a speed of 7.5 km/h. What is the magnitude of average velocity and average speed of the man over the interval of time (i) 0 to 30 min (ii) 0 to 50 min (iii) 0 to 40 min ?

Explanation

Distance travelled from 30 to 50 min `=7.5xx 20"/"60= 2.5 km`. Total distance in 0 to 50 min `=2.5+2.5= 5km`.
Total time `=5"/"6h`. Average speed `= 5km"/"(5"/"6)h = 6kmh^(-1)`.
The displacement for the interval 0 to 50 min is zero. Hence velocity is zero.