A man walks on a straight road from his home to a market ` 2.5 km` away with a 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 (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 min ?

Explanation

Time taken by man to go from his home to market, 1 `t=("distance")/("speed") =(2.5)/(5) =(1)/(2) hr =30` min
Time taken by man to go from market to his home, `t_(2) =(2.5)/(7.5) =(1)/(3) hr =20` min
? Total time taken `t_(1)+t_(2)=(1)/(2) +(1)/(3)=(5)/(6) hr =50` min
0 t 50 min
Total distane traveled =2.5 +2.5 =5 km
Total displacement = zero
(a) Average velocity `=("displacement")/("time") =0`
(b) Average speed `=("distance")/("time") =(5)/(5//6) =6 km//hr`