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# Shot Velocity Question

07-02-2010, 03:36 AM
#26
Giroux tha Damaja
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Quote:
 Originally Posted by donGjohnson I'm no physicist, but I always see higher speed when shooting lighter objects. I've also found that true when throwing things, generally. Obviously however, they cause less force of impact. I think it's no coincidence, though I can't recall the specific term for this, I'm pretty sure there is one...
One is velocity (speed), and the other is momentum (speed x mass). Makes perfect sense.

 07-02-2010, 08:00 AM #27 kakemono Registered User   Join Date: Dec 2006 Posts: 905 vCash: 500 Momentum (Mass x Velocity) is conserved. (Stick x Velovity) = (Puck x Velocity). Decrease Puck weight, increase Velocity. That is the answer to the perfect, closed system question. That said, the biggest I see is the compression of the puck. Some of the velocity of the stick will go into compressing the puck and I don't know the difference in dynamics of the two pucks. Will the heavier puck compress more and thus provide more of a launch off the the stick? I don't know.
07-02-2010, 08:05 AM
#28
Crosbyfan
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Quote:
 Originally Posted by I am The Mush I agree with you 100%. Momentum is measured in Joules. Mass x Velocity gives momentum. If you release the same number of Joules of energy into two stationary pucks they both end up with the same momentum. .
Momentum is not measured in Joules. Mass x Velocity does give momentum. Kinetic energy, 1/2 mass X velocity squared,(can be measured in Joules) and momentum are not the same thing.

If you release the same number of Joules of energy into two stationary pucks with different mass they both cannot end up with the same momentum.

07-02-2010, 11:09 AM
#29
Gino 14
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 Originally Posted by Orange Crush 89 All right, this might seem like a stupid question, but there's nothing wrong with asking. Heck, there may not even be a scientific answer, but anyway... Does the weight of a puck bear any effect on the velocity of a shot? For example; what would the difference be between the clocked speed of a floor hockey puck (roughly 0.9oz) vs a street or ice hockey puck (roughly 5.5/6.0oz)? Would it be faster, slower or no significant difference?
Since weight is not a factor in velocity (v = d x t), a clocked speed of 60 mph for a floor hockey puck is exactly the same as a clocked speed of 60 mph for an ice hockey puck.

07-02-2010, 01:27 PM
#30
Giroux tha Damaja
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Quote:
 Originally Posted by Crosbyfan Momentum is not measured in Joules. Mass x Velocity does give momentum. Kinetic energy, 1/2 mass X velocity squared,(can be measured in Joules) and momentum are not the same thing.
Whoops, (Kg-meters)/second is the measurement for momentum.

Quote:
 Originally Posted by Crosbyfan If you release the same number of Joules of energy into two stationary pucks with different mass they both cannot end up with the same momentum.
D'oh, I have committed the classic beginner-physicist's mistake of interchanging momentum and kinetic energy (which obviously doesn't work since ½ m*v^2 =/= mv, except for certain specific sets of numbers). I should have known better.

That said, if you subject two pucks to the same impulse, it still holds true that the heavier puck is going to have less velocity than the lighter puck. The extent to which this is true would be less than I was saying, due to the differences in the equations used, but it is still true in a qualitative sense which is all we're trying to get at here (not to say that I don't appreciate you highlighting the distinction and my mistake).

 07-06-2010, 02:58 PM #31 Hounsy Registered User   Join Date: Dec 2003 Location: A wonderful location Posts: 1,671 vCash: 572 Would the puck hold it's velocity better due to more weight? As a goalie it feels like it does. Meaning the ball may have a higher peak but the puck may have a better average over the distance?
 07-06-2010, 03:17 PM #32 TBLfan Registered User     Join Date: Nov 2005 Location: Tampa, FL Posts: 1,148 vCash: 500 Goalies tend to "feel" pucks more when they spin faster. Same shot speed but certain players shoot heavier. Same thing with baseball, some guys pitches feel heavier, it's almost feels like hitting a small bowling ball. Those pitchers are generally known to break more bats. Goalies, in pads, won't feel a roller hockey ball but they feel pucks depending on speed and "heaviness" of the shot.. I dont think I've ever heard of any goalie complain about an inline puck without it making it through the padding but I've definitely seen goalies go down from a shot on ice. I've taken down a friend of mine more than once... always feel bad too.
 07-06-2010, 06:46 PM #33 SEALBound Fancy Conor McSheary     Join Date: Jun 2010 Posts: 21,497 vCash: 500 Jebus. Straight, no BS answer: Yes, given the same shot, the light puck will go faster.
07-06-2010, 07:57 PM
#34
Crosbyfan
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Quote:
 Originally Posted by SEALBound Jebus. Straight, no BS answer: Yes, given the same shot, the light puck will go faster.
Same shot is not the same...

Why didn't we think of that?

 07-06-2010, 08:51 PM #35 ponder Registered User     Join Date: Jul 2007 Location: Vancouver Country: Posts: 13,119 vCash: 500 A lighter puck will leave your stick at a faster speed (you're applying the same force to less mass, so there will be more acceleration), but will also be slowed down more by air resistance after it leaves you stick. In general, at normal distances, I definitely think my shot is faster with the light street hockey pucks, but if you were to measure the speed on some ridiculous full rink slap shot, I could see the heavier puck being faster at the end due to being slowed down significantly less by air resistance.

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