When a driver of Shatabdi Express, running with velocity 108 km/hr, sights a goods train going ahead of him at a distance 50 m in the same direction on the same track, running with velocity 72 km/hr, he applies brakes. In order to avoid an accident, what should be the magnitude of the deceleration produced by the brakes?

When a driver of Shatabdi Express, running with velocity 108 km/hr, si

1.	When a driver of Shatabdi Express, running with velocity 108 km/hr, sights a goods train going ahead of him at a distance 50 m in the same direction on the same track, running with velocity 72 km/hr, he applies brakes. In order to avoid an accident, what should be the magnitude of the deceleration produced by the brakes?
Answer» `5 ms ^(-2) ` `1 ms ^(-2)` `3 ms ^(-2)` None of these Solution :`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)`