An object moving on a straight line covers first half of the distance at speed v and second half at speed 2v. Find -

(i) Average speed
(ii) Mean speed

Explanation

(i) Let total distance =D.
So, time taken to cover the first half = `(D//2)/(v)=(D)/(2v)`, and time taken to cover the second half `(D//2)/(2v)=(D)/(4v)`
Hence average speed `("total distance")/("total time")`
`=(D)/((D)/(2v)+(D)/(4v))=(D)/(D((2+1)/(4v)))=(4v)/(3)`
(ii) Mean speed = `(v+2v)/(2)=(3v)/(2)`