1.

Train covers half of its journey with speed of 30 M per second and other half with a speed of 40 metre per second calculate average speed of train during whole journey

Answer»

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)


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