A2 kg piece of ice moving in the +x direction at 4.0
m/sstrikes a 3 kg piece of ice that is initially at rest. after
thecollision, the 2 kg piece moves at an angle of 40degrees above
the+x axis at a speed of 1.9 m/s. find magnitude and direction of
thevelocity of the 4 kg piece.

Explanation:

velocity of first piece

mass of second piece

Velocity of second piece

After collision 2 kg mass deviate 40 degree from x axis

Let m/s be the velocity of 2 kg piece and be the of second Piece  after collision

Conserving momentum in x direction

------1

Conserving Momentum in Y direction

-------2  

squaring and then adding 1 & 2 we get

for direction divide 1 and 2 we get

i would say