Train with Train!
Classical Mechanics
Level
pending
Two trains move on straight parallel tracks with uniform speed 40 km/h and 30 km/h.Time taken to cross each other is t1,if they are in the same direction and t2 ,if they are in the opposite direction .Then t1 : t2?
3:4
1:7
4:3
7:1
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1 solution
THE FORMULA FOR RELATIVE SPEED IS =INITIAL GAP/DISTANCE REDUCED PER UNIT TIME, i.e. IN 1 HOUR THE GAP BETWEEN THE FIRST CAR AND SECOND CAR WILL BE 10KMS. AND DISTANCE REDUCED PER UNIT TIME WILL ALSO BE 10KMS. THEREFORE t1=1.
NOW t2, USING THE FORMULA INITIAL GAP IN 1HR BETWEEN BOTH THE TRAINS/RESPECTIVE SPEED,i.e {40KMS.-30KMS.}./ {30KMPH +40KMPH}=10/70,i.e.1/7.
THEREFORE T1:T2=1/1/7,i.e.7:1