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Hockey Stick Momentum problem

  • Thread starter Precursor
  • Start date
  • #1
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Homework Statement


Two 72.0 kg hockey players skating at 5.45 m/s collide and stick together. If the angle between their initial directions was 115[tex]^{o}[/tex], what is their speed after the collision?


Homework Equations


p = mv

[tex]p_{i} = p_{f}[/tex]


The Attempt at a Solution



Here's my interpretation of the image;

http://img696.imageshack.us/img696/1493/momentum.png [Broken]

[tex]p_{ix} = p_{fx} = 0[/tex]

[tex]p_{iy} = p_{fy}[/tex]

[tex]m_{A}v_{A} + m_{B}v_{B} = (m_{AB})(v_{AB})[/tex]

[tex](72)(5.45cos(32.5)) + (72)(5.45cos(32.5)) = 144v_{AB}[/tex]

[tex]v_{AB} = 4.60 m/s[/tex]

Am I correct?
 
Last edited by a moderator:

Answers and Replies

  • #2
rl.bhat
Homework Helper
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P*cosθ components of the two players get canceled according to the diagram given by you . Check the other components. Your calculation will be correct if you use θ = 57.5 degrees.
 
  • #3
222
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P*cosθ components of the two players get canceled according to the diagram given by you . Check the other components. Your calculation will be correct if you use θ = 57.5 degrees.
Oh, so I need to use sin instead?
 
  • #4
rl.bhat
Homework Helper
4,433
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Oh, so I need to use sin instead?
For your mentioned angle, yes.
 
  • #5
222
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Ok, so the new answer is 2.93 m/s.

Thanks for the help
 

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