Question

During the course of motion along a straight road,A man covers first 'd' distance with velocity 'v' next '2d' distance with velocity '4v' and final distance d' with velocity v Average speed for complete motion is

Answer 1

we know that
average speed=total distance\total time taken

so total distance =d+2d+d=4d
time taken while moving with velocity d= d\v
again time taken while moving with velocity 4v=2d/4v=d/2v
again time taken while moving with velocity v=d/v
total time taken=d/v+d/2v+d/v=5d/2v
average speed=4d×2v/5d=8v/5