Bullet blocks problem

1. The problem statement, all variables and given/known data

A block A of mass MA = 1 kg is kept on a smooth horizontal surface and attached by a light thread to another block B of mass MB=2 kg .Block B is resting on ground and thread and pulley are massless and frictionless.A bullet of mass m 0.25 kg moving horizontally with velocity of u=200m/s penetrates through the block and comes out with a velocity of 100m/s.Find the height through which the block B will rise.

Ans :5.25m

2. Relevant equations

3. The attempt at a solution

When bullet penetrates through block A ,an impulsive force P acts on it.

∫Pdt = 0.25(200-100) = 25Ns

Considering block A,let the impulsive tension be T

∫Pdt – ∫Tdt = 1(vA)

Considering block B ,

∫Tdt = 2vB

I guess I am missing something ,is it vA = vB because of inextensibility of the string connecting the masses? But that doesn’t give correct answer .

I would be grateful if somebody could help me with the problem.

Attached Images
File Type: gif blocks.GIF (27.8 KB)

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