Question

Driver of a train travelling at $115km/h$ sees on a same track, $100m$ infront of him, a slow train travelling in the same direction at $25km/h$. The least retardation that must be appiled to faster train to avoid a collision is

• A. $3.125m/s^2$
• B. $3.5m/s^2$
• C. $2.75m/s^2$
• D. $3.0m/s^2$

Answer 1

The correct option is A $3.125m/s^2$

Velocity of train 'B' with respect to train 'A' = $(115-25)km/h$

$V_{BA}=-90km/h$ $=-25m/s$

Distance between the trains is $100m$. Using the equations of motion

$v^2=u^2-2as$ $,v=0$

$u^2=2as$

$625=2\times a\times 100$

Then the least retardation that must be appiled to faster train to avoid a collision, $a=3.125m/s^2$