Question

A train covers half of its journey with the speed of 30metre per second and other half with the speed of 40metre per second calculate it's average speed for the entire journey

Answer 1

Let the distance be 2d.
& let The time be t.
Case1:
Distance (1)=d
Speed (1)=30m/s
:.Time(1)=distance(1)/speed(1)
=D/30
Case2:
Distance (2)=d
Speed(2)=40
:. Time (2)=distance (2)/speed(2)
=D/40
Now,
Average speed=total distance/total time
=(d+d)/{t(1)+t(2)}
=2d/(d/30+d/40)
=2d/(40d+30d)/(30×40)
=2d/70d/1200
=(2d×1200)/70d
=2400d/70d
=2400/70
=34.29m/s
(ÆÑẞWĒR)