[حمدى محمد]

Change in momentum is very easy to calculate. Momentum is mass times velocity. The only thing changing is velocity since mass is constant, so it can be written as: M2 - M1 = Change in momentum

But the mass is constant, so you just calculate the momentum at both times..

M1 = 2.0 kg x 2.0 m/s = 4.0 kg*m/s
M2 = 2.0 kg x 1.5 m/s = 3.0 kg*m/s

Now subtract the two for your answer.

4.0 kg*m/s - 3.0 kg*m/s = 1.0 kg*m/s

The change in momentum is 1 kg per meter per second