A car completes its journey in a straight line in three equal parts with speeds `v_1,v_2 and v_3` respectively. The average speed `v` is given by :

Options

A. `(v_(1) + v_(2) + v_(3))/(3)`
B. `sqrt(v_(1) v_(2) v_(3))`
C. `(1)/(v) = (1)/(v_(1)) + (1)/( v_(2)) + (1)/( v_(3))`
D. `(3)/(v) = (1)/(v_(1)) + (1)/(v_(2)) + (1)/(v_(3))`

Answer

D

Explanation

Average speed `v = ("Total distance ")/("Total time")`
`rArr v = (s)/((s//3)/(v_(1))+(s //3)/(v_(2))+(s//3)/(v_(3))) = (3)/((1)/(v_(1)) + (1)/(v_(2)) + (1)/(v_(3)))`
`rArr (3)/( v) = (1)/(v_(1)) + (1)/(v_(2)) + (1)/(v_(2))`