Momentum vectors (add and subtract)

[huybinhs]

Homework Statement

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 please help with P1 - P2.

Thanks!

 

[AC130Nav]

Homework Statement

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 please 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! ;)