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

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the box does not move because you need to use a force greater than 300 n. you are only using 50 n. it needs to at least be 301 n for the box to move because then it is an unbalanced force and it will move the way that the greater force is pushing it. if you use only 300 n it will be a balanced force and will not move because the force you are exerting on the   box is the same as its force.

hope this !

im sorry if i went too in depth, i am going to include a link to a video on khan academy that will explain this.   hope that you like the video and that it explains more in detail to you.

that is the link.