question_answer 14)

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

Answer:

                Case (i): 0 to 30 mm Speed Distance covered in 30 min   Displacement covered = 2.5 km (a) Average velocity          . (b) Average speed . Case (ii): 0 to 50 min Displacement covered in first 30 min in going to market   Displacement covered in next 20 min in coming back to home   Net displacement = 2.5 - 2.5 = 0 Total distance covered = 2.5 + 2.5 = 5 km (a) Average velocity (b) Average speed Case (iii): 0 to 40 min Displacement covered in first 30 min in going to market =2.5 km Displacement covered in next 10 min in coming bad to home   Net displacement = 2.5- 1.25= 1.25 km Total distance travelled == 2.5 + 1.25= 3.75 km (a) Average velocity (b) Average speed