Velocity and Direction of a System after Inelastic Collision

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SUMMARY

The discussion centers on an inelastic collision involving a hockey player and a puck, where the player has a mass of 30.0 kg and moves at 2.00 m/s, while the puck has a mass of 0.18 kg and moves at 35.0 m/s at a 60-degree angle. The calculated post-collision speed is 1.89 m/s at an angle of 5.48 degrees. The collision is classified as inelastic since the kinetic energy after the collision is less than before, confirming energy loss.

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  • Understanding of momentum conservation principles
  • Knowledge of kinetic energy calculations
  • Ability to resolve vectors into components
  • Familiarity with inelastic collision characteristics
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  • Study the principles of inelastic collisions in physics
  • Learn how to calculate resultant vectors from components
  • Explore examples of kinetic energy loss in collisions
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Students studying physics, particularly those focusing on mechanics and collision theory, as well as educators seeking to explain inelastic collisions and momentum conservation.

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Homework Statement


A hockey player with a mass of 30.0-kg is initially moving 2.00-m/s to the right. He catches on the stick a puck initially moving at 35.0-m/s at an angle of 60 degrees. The puck's mass is .18 kg and the player and puck form a single object for a few seconds. (A) Determine the direction angle and speed of the puck AND skater after the collision. (B) Was this collision elastic or inelastic? Prove it with numbers.
http://imgur.com/q8IDYQb
SORRY FOR THE TERRIBLE DRAWING... kind of in a hurry.

2. Homework Equations

Pbefore = Pafter >>> MV + mv = (M+m)V
Conservation of kinetic energy and 1/2mv2

The Attempt at a Solution


The answers are given:
(A): 1.89-m/s , 5.48 degrees
(B): inelastic because K < K0

I understand B, mostly. You just find the kinetic energies of the systems before and after and compare them. If they don't match up, it has lost some KE and you know it's inelastic. But, part A really messes me up. I tried just plugging in the numbers for my first relevant equation, then I realized I probably needed to find the components of each and then find the resultant ones. Any help would be amazing.
-TP
 
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First, let me say this is a terrible problem. A hockey player is not an inert object that gets knocked around by a puck. He could stop a puck without moving if he wanted to. It's not that different from stopping a soccer ball without getting knocked backwards.

That said, if you imagine the player has no grip on the ice, you need to use momentum conservation in two directions for part A.
 
You cannot use energy because you do not know how much was lost, so you need another equation. You are told that the two form a single object for a while. What equation does that give you?
With regards to @PeroK's critique, I offer a slightly different view. A reasonable supposition is that a skater has negligible friction in the direction of travel, but will never slide orthogonally to that. On that basis, you could use conservation of momentum in the skater's original direction, but assume the skater's direction does not change. Whether that is what the question intends I cannot tell.
 

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