The spring constant k = 700 N/m. The masses mA = 14 kg and mB = 18 kg. The horizontal bar...

The initial and final positions of the system are as shown in the figure

The stretch in the spring can be obtained from the following figure

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When block moves 0.2 m downward, collar ‘A’ slides 0.2 m in horizontal direction and we have

The change in length of the spring (as the spring is initially un-stretched) is given by

Using conservation of energy for the system at positions 1 and 2, we get

Solving for the velocity, we get

Thus, the velocity of the block after the initial displacement is equal to