A Physics teacher is explaining the difference between average speed and average velocity to her students.
Where average velocity `= ("displacement")/("time taken")`, `"average speed" = ("actual distance travelled")/("time taken")`
She emphasises that average speed is more relevant than average velocity, because displacement from one place to other is only theoretical, being the shortest distance between two places. Average speed is the real entity that matters, taking into account the actual time taken to travel the actual distance between the two stations.
Read the above passage and answer the following question :
(i) Do you agree with the statement of Physics teacher ?
(ii) The shortest distance between Ambala to Delhi is `200 km`. A train takes `4 hrs` and covers a distance of `210 km` in going from Ambala to Delhi via Karnal. Another train takes `5 hrs` and covers `250 km` distance in going from Ambala to Delhi via Saharanpur. What is the average speed of these two trains? What would be the average velocity of a train that takes `2.5 hrs` to cover `200 km` distance ?
(iii) What values do you learn from this discussion ?

Explanation

(i) Yes, we agree with the statement of Physics teacher.
(ii) Average speed of first train `= ("distance travelled")/("time taken") = (210 km)/(4 hrs) = 52.5 km//hr`
Average speed of second train `= (250 km)/(5 hrs) = 50 km//hr`
Average velocity of train `= ("displacement")/("time") = (200 km)/(2.5 hr) = 80 km//hr`
(iii) From the above discussions, we learn that if two places, say `A` and `B` between which we have to travel are connected by different routes, we should choose the route in which we have to travel the minimum distance , and along which road conditions are good. This would save us time and also the cost of travel. We can advise our friends accordingly and fulfil our social obligations.