How Is the Initial Momentum of a 2kg Block Determined After Explosion?

[kaitamasaki]

Homework Statement

A 2 kg block moves north at an unknown velocity. It then explodes into two blocks, the first one being 1.2 kg and moves EAST at 10 m/s, the second one is 0.8 kg and moves 22 m/s at an angle North of West.

What is the initial MOMENTUM of the 2kg block?

Homework Equations

p initial = p final (momentum conserved)

The Attempt at a Solution

The answer i got was 13 kg m/s, and some friends of mine got 29.6 kg m/s. The reason i got 13 is because I think/thought the two horizontal components of the exploded blocks cancel out each other because they are in separate directions (velocity is a vector and therefore one being negative one being positive, so I thought only the vertical component of the second block's momentum mattered).

Any help is appreciated Thank You!

 

[Doc Al]

You are correct; your friend is not. Good reasoning.