Question

two trains one travelling at 72 km per hour and the other at 90 km per hour or heading towards one and another along a straight level track when they are 1.0 Km apart both the drive simultaneously other train and apply the brakes it at each other at the rate of the 1.0 metre per second it remind whether the train would eat or not

Answer 1

velocity of train 1

$v_1 = 72 kmph$

$v_1 = 20 m/s$

now velocity of 2nd train

$v_2 = 90 kmph$

$v_2 = 25 m/s$

deceleration of both trains is given by

$a = -1 m/s^2$

now we can find relative velocity of two trains

$v_{12} = v_1 - v_2$

$v_{12} = 20 - (-25) = 45 m/s$

relative acceleration of two trains

$a_{12} = -1 -1 = -2 m/s^2$

now distance by which two trains stop relative to each other

$v_f^2 - v_i^2 = 2 a s$

$0 - 45^2 = 2*(-2)s$

$s= 506.25 m$

so two trains will stop before they collide because the distance after which they stop is 506.25 m and the initial distance was 1 km = 1000 m.

Answer 2

Answer:

The answer is given above.