# Momentum vectors (add and subtract)

#### huybinhs

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

P1x = 7 * 0.5 = 3.5 kg m/s ; P1y = 4*0.5 = 2 kg m/s => P1 = sqrt (3.5^2 + 2^2) = 4.03N*s

so P2 = 2.92 kg m/s ; and P3 = 2.69 kg m/s

then the question #2 is:

P1 + P2 = sqrt (4.03^2 + 2.92^2) = 4.98 kg m/s

P1 - P2 = I have no ideas.

Is my work correct? and plz help with P1 - P2.

Thanks!

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#### AC130Nav

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

I did:

P1x = 7 * 0.5 = 3.5 kg m/s ; P1y = 4*0.5 = 2 kg m/s => P1 = sqrt (3.5^2 + 2^2) = 4.03N*s

so P2 = 2.92 kg m/s ; and P3 = 2.69 kg m/s

then the question #2 is:

P1 + P2 = sqrt (4.03^2 + 2.92^2) = 4.98 kg m/s

P1 - P2 = I have no ideas.

Is my work correct? and plz help with P1 - P2.

Thanks!
Vectors are added head to tail. For P1 + P2 you seem to be working on the wrong triangle.
I guess P1 - P2 is question #3? To subtract P2 you reverse its direction, then add as noted.

#### huybinhs

Got it! Thanks! ;)

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