A person travelling in a straight line moves with a constant velocity v1 for certain distance x and with a constant velocity v2 for next equal distance. The average velocity v is given by the relation    [NEET 2019]

For distance x, the person moves with constant velocity v1 and for another x distance, he moves with constant velocity of v2 thenTotal distance travelled by the person,                     D = x + x = 2xTotal time taken to cover that distance,,                    T=t1+t2=xv1+xv2                      ∵t= Distance  Velocity Average velocity,                    vav= Total distance  Total time =DT                     v=2xxv1+xv2=21v1+1v2                            ∵vav=v⇒                    2v=1v1+1v2