A man walks on a straight road from his home to a market 2.5 km away with speed of 5 `\frac { k m } { h \r }`. Finding the market closed, he instantly turns and walks back home with a speed of 7.5 `\frac { k m } { h \r }`. The average speed of the man over the interval of time 0 to 40 min is equal to

Explanation

Time taken by woman to go from her home to market
`t_(1) =("Distance") /("Speed") = (2.5)/(5) = (1)/(2)` h
Time taken by woman to go from market to her home,
`t_(2) = (2.5)/(7 . 5) = (1)/(3) h`
`:.` Total time `= t_(1) + t_(2) = (1)/(2) +(1)/(3) = (5)/(6)` h
=50 min
(a) Average velocity
`vec(v) _(av) = ("Displacement")/("Time")`
(b) Average sped
`v_(av) = ("Distance")/("Time") `
Between 0 to 30 min
`vec(v) _(av) = (2.5)/((1)/(2))`
= 5 km /h towards market