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Angle from force applied / Momentum question

  1. Mar 3, 2009 #1
    1. The problem statement, all variables and given/known data

    Okay the first question is:

    1. A hockey puck with mass 0.250 kg has initial velocity 3.00 i + 5.00 j m/s just before being hit by a hockey stick. The final velocity after the hit is -37.0 i + 25.0 j m/s. What was the magnitude of the impulse delivered by the stick to the puck, in kg m/s?

    For this I just took the final velocity - initial and took the magnitude to get .250 sqrt[-40^2 + 20^2] = 11.18

    Part two though I have no idea how to do.

    2. What is the angle of the force applied to the hockey puck in the previous problem? The angle should be measured with respect to the positive x-axis in degrees.

    below.

    3. Is it possible for the total momentum of three particles to be zero, even though the momentum of the individual particles is not?

    below.

    2. Relevant equations

    p= mv
    Velocityf - Velocityi

    3. The attempt at a solution

    2. I'm not sure how to do this.... I thought of just doing the y over x component 400/1600 = 1/4 = 45 degrees. I don't think that's right though because looking at the final velocity it looks like it will be in quadrant 2 maybe?

    3. I said yes as long as they were in the same plane because they wouldn't be able to be expressed in terms of each other. (mostly need confirmation on this yes / no)

    Thanks for your help!

    :biggrin:
     
  2. jcsd
  3. Mar 3, 2009 #2
    2. you have the direction of the initial, final velocity, and you have also calulated the direction of the impulse. Draw a vector diagram and find any angle that is necessary.
     
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