Two trans A and B 100 m and 60 m long are moving in opposite direction on parallel tracks. The velocity of the shorter train is 3 times that of the longer one. If the trains take 4s to cross each other, the velocities of the trains are

Options

A. `V_(A)=10ms^(-1),V_(B)=30ms^(-1)`
B. `V_(A)=2.5ms^(=1),V_(B)=7.5ms^(-1)`
C. `V_(A)=20ms^(-1),V_(B)=60ms^(-1)`
D. `V_(A)=5ms^(-1),V_(B)=15ms^(-1)`

Answer

A

Explanation

`{:(2V_(A)=V_(B)," "V_("rel")=V_(A)+V_(B)),(t=(I_(A)+I_(B))/(V_("rel"))," "S_(1)+S_(2)=(V_(A)+V_(B))t):}`