Question

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 :
A. `(v_1 + v_2 + v_3)/(3)`
B. `3 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 1

Correct Answer - D
Average speed, `v = ("Total distance")/("Total time")`
=`(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)/(3)`.