Answer:
Acceleration of train needed to avoid collision = -0.9 m/s²
Explanation:
Here both trains are similar with 1000 m apart with same speed.
So one train has to move 500 m before stopping just to avoid collision.
We have
Initial velocity, u = Â 30 m/s
Acceleration , a = ?
Displacement, s = 500 m
Final velocity, v = 0 m/s
We have equation of motion v²= u² + 2as
Substituting
   v²= u² + 2as
   0²= 30² + 2 x a x 500
  a = -0.9 m/s²
Acceleration of train needed to avoid collision = -0.9 m/s²