The distance between Ahmedabad and Surat is 300 km. Two trains set off simultaneously towards each other with speeds 60 km/h and 40 km/h respectively. When will they cross each other?

Options

A. 3 hours
B. 15 hours
C. `1/3` hours
D. `4/3` hours

Answer

A

Explanation

`v _(1) = (108 xx 1000)/(3600) = 30m//s, v _(2) = (72 xx 1000)/(3600) = 20 m//s.`
Initial velocity of Shatabdi Express
`v _(0) = v _(12) = v _(1) -v _(2) `
`v _(0) = 30 - 20 = 10 ms ^(-1)`
Now `v ^(2) =v _(0) ^(2) + 2ad`
Putting `v =0, v _(0) =10 ms ^(-1), d=50 m,`
`0= 100 + 2 xx a xx 50`
`therefore a xx 100 =- 100`
`therefore a =-1`
`therefore -a =1 ms ^(-2)`
`therefore` Deceleration `=1 ms ^(-2)`