Q.
The two ends of a train moving with constant acceleration pass a certain point with velocities u and v. The velocity with which the middle point of the train passes the same point is
Let the length of train is s, then by third equation of motion, v2=u2+2a×s ....(1)
Where v is final velocity after travelling a distance s with an acceleration a & u is initial velocity as per question
Let velocity of middle point of train at same point is v', then (v′)2=u2+2a×(s/2) ....(2)
By equation (1) & (2), we get v′=2v2+u2