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Shot Velocity Question

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Old
06-17-2010, 04:00 PM
  #1
Orange Crush 89
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Shot Velocity Question

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?

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06-17-2010, 04:13 PM
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Thepandamancan
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It's been a while since my physics class but I believe the lighter puck will travel faster. However, the force of your shot will be greater with the heavier puck.

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06-17-2010, 04:49 PM
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hlrsr
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Force = mass * acceleration

Assuming you put the same amount of force into your shots on both pucks, decreasing mass would increase acceleration.

I don't know that that made sense. Physics 12 was a long, long time ago.

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06-17-2010, 04:52 PM
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Jarick
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I'm not a physics expert, but my guess is the puck would have a much higher force and the same initial velocity but hold it's momentum much longer over distance.

My thinking is that the acceleration is constant (speed of the swing of the stick), but the mass is what changes, so the force is greater for the hockey puck over the street puck.

The only reason I'd think the puck would go faster over distance is the lightweight puck might flutter more with air resistance.


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06-17-2010, 05:19 PM
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AIREAYE
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Quote:
Originally Posted by hlrsr View Post
Force = mass * acceleration

Assuming you put the same amount of force into your shots on both pucks, decreasing mass would increase acceleration.

I don't know that that made sense. Physics 12 was a long, long time ago.
F= ma is only applicable in a theoretical closed system, but you've gotta factor air resistance in this one. Yes your hypothesis on mass being inversely proportional to acceleration is correct but he's asking for puck VELOCITY/Speed and not acceleration, a lighter puck would probably accelerate off a shot faster, but its terminal velocity (maximum speed) would be less that of a heavier puck (depending how much heavier), whose greater momentum (momentum = mass x velocity) would 'push it thru' air resistance easier. But again, this is all theoretical of course

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06-17-2010, 05:29 PM
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The lighter puck will start off faster. Although you should be able to apply more force to the heavier puck, it will not likely be proportional to the greater weight (mass).

So leaving the stick the lighter puck will have greater velocity.

However, the heavier puck should have more momentum, and more kinetic energy. Since drag of the pucks will be the same at any given speed (while in the air, approximately in proportion to the square of their speed), assuming they are shot the same way, so the heavier puck will hold it's speed longer and should overtake the lighter puck.

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06-17-2010, 05:35 PM
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Quote:
Originally Posted by AIREAYE View Post
F= ma is only applicable in a theoretical closed system, but you've gotta factor air resistance in this one. Yes your hypothesis on mass being inversely proportional to acceleration is correct but he's asking for puck VELOCITY/Speed and not acceleration, a lighter puck would probably accelerate off a shot faster, but its terminal velocity (maximum speed) would be less that of a heavier puck (depending how much heavier), whose greater momentum (momentum = mass x velocity) would 'push it thru' air resistance easier. But again, this is all theoretical of course
Unless shooting pucks off a cliff, terminal velocity really won't apply.

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06-17-2010, 06:09 PM
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hlrsr
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Quote:
Originally Posted by AIREAYE View Post
F= ma is only applicable in a theoretical closed system, but you've gotta factor air resistance in this one. Yes your hypothesis on mass being inversely proportional to acceleration is correct but he's asking for puck VELOCITY/Speed and not acceleration, a lighter puck would probably accelerate off a shot faster, but its terminal velocity (maximum speed) would be less that of a heavier puck (depending how much heavier), whose greater momentum (momentum = mass x velocity) would 'push it thru' air resistance easier. But again, this is all theoretical of course
yeah, high school physics is generally about closed systems.

But either way it's a relevant distinction to say that the lighter puck might travel slower because it's more susceptible to air resistance as opposed to just not initially moving as fast (less to do with the amount of force put into the shot).

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06-17-2010, 08:28 PM
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Quote:
Originally Posted by AIREAYE View Post
F= ma is only applicable in a theoretical closed system, but you've gotta factor air resistance in this one. Yes your hypothesis on mass being inversely proportional to acceleration is correct but he's asking for puck VELOCITY/Speed and not acceleration, a lighter puck would probably accelerate off a shot faster, but its terminal velocity (maximum speed) would be less that of a heavier puck (depending how much heavier), whose greater momentum (momentum = mass x velocity) would 'push it thru' air resistance easier. But again, this is all theoretical of course
So in English, it is easier (takes less force) to shoot (accelerate) an inline puck. So if you gave a guy a two pucks, he probably shoots the inline puck harder. The difference in speed between the two would probably decrease as the stiffness of the stick and strength of the shooter increased.



You comment on the terminal velocity of the puck isn't really very relevant, since the puck wouldn't be under a constant accelerative force. So it's not like it would continuously gain speed up to the point where the force of drag = the force of acceleration.

The terminal velocity of a puck falling downwards under the influence of gravity is probably ~60mph, so I would imagine the terminal velocity under the kind of acceleration it gets from a stick would be in the high 3, low 4 digit range. But it's irrelevant since the motion of shooting doesn't provide steady acceleration, it's a pulse.


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06-17-2010, 08:29 PM
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These are all great answers (and information) and I really appreciate it. My guess, beforehand, would have been that you'd be able to slap an actual puck harder and faster than a lighter, floor hockey puck, but now my thoughts are mixed. I suppose, ultimately, the only way to gauge a difference would be to clock both.

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06-17-2010, 08:32 PM
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Quote:
Originally Posted by hlrsr View Post
yeah, high school physics is generally about closed systems.

But either way it's a relevant distinction to say that the lighter puck might travel slower because it's more susceptible to air resistance as opposed to just not initially moving as fast (less to do with the amount of force put into the shot).
Assuming an ice and inline puck are traveling the same rate, the lighter puck has less momentum (mass * velocity), due to it's lesser mass. That would translate into the puck decelerating at a greater rate as it traveled through the air (this is making the fair assumption that the drag on both pucks would be roughly equal).

So in short, given an equal shooting motion, the inline puck should leave the blade of the stick traveling at a greater speed, but lose that speed faster than an ice puck will.

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06-17-2010, 09:04 PM
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blackcharger
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All valid points,but it will require a greater force to get the same initial speed on the heavier puck.Think of throwing it.There is no way you could throw the heavier one faster.Also the stick's flex would change things up.Heavier puck would cause more of a flex and would that compensate for the wieght difference.I would like to see some actual numbers for proof.

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06-18-2010, 02:08 AM
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HowToHockey
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Time to go Scientific

First a test. My friend and I hammered some slappers with a puck and with a road hockey ball. The ball went a lot faster, I think about 5-10 MPH faster.

Next real science.

Here is a study I found a while back

http://www.springerlink.com/content/y725633rn2r8r67h/

and here is a quote from the abstract

"It was concluded that decreased stick stiffness and puck weight increased puck velocity in standing slap shots for female ice hockey players. "

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06-18-2010, 06:21 AM
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Quote:
Originally Posted by blackcharger View Post
All valid points,but it will require a greater force to get the same initial speed on the heavier puck.
This falls in line with what I was saying. Inline puck = greater initial velocity, greater deceleration due to drag. Ice puck = lower initial velocity, less loss of velocity due to drag.


Quote:
Originally Posted by blackcharger View Post
Think of throwing it.There is no way you could throw the heavier one faster.

This is true. But you could almost certainly throw the heavier puck just as fast. The reason being, what is limiting your arm speed at the release point is not nearly so much the mass of the puck as it is the limits of your body and the inherent inefficiency of the throwing motion. I doubt pitchers could throw a golf ball any faster than they could throw a baseball.

Quote:
Originally Posted by blackcharger View Post
Also the stick's flex would change things up.Heavier puck would cause more of a flex and would that compensate for the weight difference.I would like to see some actual numbers for proof.
It is almost entirely the resistance of the shooting surface that loads the stick before contact with the puck (which is why good shooters make contact with the ice behind the puck). The resistance of the floor is a normative force (i.e. it will increase up to infinity to match precisely the amount of downward force you're exerting on the stick against it). So it is the strength (and after a certain point, the weight) of the shooter that are the limiting factors in a shooter's ability to load the stick, not the mass of the puck. If you were able to obtain a perfect shooting motion (perfect in the sense that you just want max velocity, not accounting for aim), the stick would stop flexing (storing potential energy) and begin to whip back (transferring kinetic energy to the puck) at precisely the point it contacted the puck. Any time you spend contacting the puck and flexing the stick is time that the blade isn't unloading energy into the puck.

Now people's anatomy isn't perfect for shooting hockey pucks so in practice there is a brief time when the blade touches the puck that it is not free to unload, but the principles involved hold true.


Last edited by Giroux tha Damaja: 06-22-2010 at 08:40 AM. Reason: typo
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06-18-2010, 06:27 AM
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Quote:
Originally Posted by beavboyz View Post
Here is a study I found a while back

http://www.springerlink.com/content/y725633rn2r8r67h/

and here is a quote from the abstract

"It was concluded that decreased stick stiffness and puck weight increased puck velocity in standing slap shots for female ice hockey players. "
I think they would have found, had they gotten some very good, very strong shooters, is that up to the point the shooters were no longer strong enough to get a lot of flex in the stick, that a stiffer stick would create a harder shot. Reason being that a stiff stick that is bent back X degrees is storing a greater amount of potential energy than a whippy one at X degrees. The ladies involved probably weren't big enough to load the stiffer sticks with an efficient shooting motion (they're also probably using shorter sticks, so the speed of the blade as they go through the motion, discounting the effect of flex, is slower too).

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06-22-2010, 06:42 PM
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Quote:
Originally Posted by I am The Mush View Post
I think they would have found, had they gotten some very good, very strong shooters, is that up to the point the shooters were no longer strong enough to get a lot of flex in the stick, that a stiffer stick would create a harder shot. Reason being that a stiff stick that is bent back X degrees is storing a greater amount of potential energy than a whippy one at X degrees. The ladies involved probably weren't big enough to load the stiffer sticks with an efficient shooting motion (they're also probably using shorter sticks, so the speed of the blade as they go through the motion, discounting the effect of flex, is slower too).
sort of similar to the pounds of pressure when shooting a crossbow, the more pounds the harder it is to pull back, but the harder you can shoot it. Obviously lower pounds for weaker people.

I think though that a lighter puck would go faster.

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06-22-2010, 06:59 PM
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You also have to take into consideration the effect that the weight of the puck has on the torque of the stick. Granted you derive most of your stick torque from the ground, but the puck still aides a little.

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06-22-2010, 08:11 PM
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Slower, because of air resistance. I would guess that since the light plastic puck is going to have a very short impulse time (it will leave almost immediately after it is made contact with the stick), it won't be on long enough to accelerate. The heavy puck has a longer impulse time, since it is heavier, so it has more time to accelerate as the stick pushes it along at a longer distance and a bigger rebound from the stick flex.

Weaker players will probably get more on the shot with the plastic puck, but there would be a point where stronger players overcome that and will get a lot more on the real puck.

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06-23-2010, 03:18 AM
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I can tell you from personal experieince that while shooting the blue kiddie lightweight pucks I shoot a much faster slapshot.

They weigh 4oz and seem to rip really well. Maybe it just feels like that compared to the heavier black pucks.

Good question here honestly.

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06-23-2010, 07:45 AM
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Quote:
Originally Posted by beavboyz View Post
sort of similar to the pounds of pressure when shooting a crossbow, the more pounds the harder it is to pull back, but the harder you can shoot it. Obviously lower pounds for weaker people.

I think though that a lighter puck would go faster.
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. The difference is that the lighter puck has to travel faster than the heavy puck to have equivalent momentum. So the lighter puck will go faster.

I can say that I find this to be true from playing goal. Guys with decent shots with an ice puck absolutely rip the inline puck. Their releases always seem faster (and harder to read because of it) with the inline puck as well. This is probably because the stick is taking less time to complete it whipping motion and release the inline puck....which means its moving faster to complete the motion in less time, meaning <drum roll> the light puck goes faster.

Quote:
Originally Posted by Razzmatazz View Post
Slower, because of air resistance. I would guess that since the light plastic puck is going to have a very short impulse time (it will leave almost immediately after it is made contact with the stick), it won't be on long enough to accelerate. The heavy puck has a longer impulse time, since it is heavier, so it has more time to accelerate as the stick pushes it along at a longer distance and a bigger rebound from the stick flex.

Weaker players will probably get more on the shot with the plastic puck, but there would be a point where stronger players overcome that and will get a lot more on the real puck.
I think that both pucks would stay on the blade for the time it took for entirety of the sticks whipping motion to complete. That would allow for equal transfer of energy. It would just take slightly longer for the stick to impart all it's energy into the heavier puck.

When you want to look at the final velocity from an accelerative force (impulse or otherwise), it is not just the duration of the acceleration, but also the magnitude of acceleration. The duration of an impulse between a baseball bat and a baseball is far shorter than between a stick and puck, but it is a far more powerful impulse, which is why a bat changes the velocity of a ball by ~150mph in a tiny fraction of a second. It isn't just duration you consider, but magnitude.

If the impulse time is shorter with a lighter puck, it will be only because the stick has completed whipping back to its original shape slightly faster due to less resistance to acceleration from the mass of the puck.........which means the blade (and puck) accelerated harder and reached a higher max speed than with a heavy puck before regaining it's original shape. Which is confirmed by some of the experiences in this thread.

So even though the impulse will be a bit shorter with a light puck, it will also have a bit higher peak acceleration. The impulse of the stick when shooting a heavy puck and a light puck should release almost exactly the same # of joules of kinetic energy into the pucks, though the shape of the curves of the two impulses would be slightly different. The stick is doing the same amount of work regardless of impulse duration.


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06-23-2010, 07:52 AM
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Razzmatazz
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Quote:
Originally Posted by I am The Mush View Post
I agree 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. The difference is that the lighter puck has to travel faster than the heavy puck to have equivalent momentum. So the lighter puck will go faster.



I think that both pucks would stay on the blade for the time it took for entirety of the sticks whipping motion to complete. That would allow for equivalent transfer of energy. It would just take slightly longer for the stick to impart all it's energy into the heavier puck.

When you want to look at the final velocity from an accelerative force (impulse or otherwise), it is not just the duration of the acceleration, but also the magnitude of acceleration. The duration of an impulse between a baseball bat and a baseball is far shorter than between a stick and puck, but it is a far more powerful impulse, which is why a bat changes the velocity of a ball by ~150mph in a fraction of a second. It isn't just duration you consider, but magnitude.

If the impulse time is shorter with a lighter puck, it will be only because the stick has completed whipping back to its original shape slightly faster due to less resistance from the mass of the puck.........which means the blade accelerated harder and reached a higher max speed than with a heavy puck. Which is confirmed by some of the results shown in this thread.

So even though the impulse will be a bit shorter with a light puck, it will also have a bit higher peak acceleration. The impulse of the stick when shooting a heavy puck and a light puck should release almost exactly the same # of joules of kinetic energy into the pucks, though the shape of the curves of the two impulses would be slightly different. The stick is doing the same amount of work regardless of impulse duration.
That's why I added that last disclaimer. I think the maximum speed attainable would be with the real puck...there are a lot of variables in between that would determine one or the other....it is certainly easier to make the plastic puck go faster with less technique, but someone with great technique and a stiffer stick can probably get a lot more onto the real puck if they have the strength to flex the stick.

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06-23-2010, 08:18 AM
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Quote:
Originally Posted by Razzmatazz View Post
That's why I added that last disclaimer. I think the maximum speed attainable would be with the real puck...there are a lot of variables in between that would determine one or the other....it is certainly easier to make the plastic puck go faster with less technique, but someone with great technique and a stiffer stick can probably get a lot more onto the real puck if they have the strength to flex the stick.
If the mass of the puck had more to do with how much energy you could load into the stick, I would agree. As it is the limiting factors there are the strength and weight of the player to force the stick to bend. By the time you have increased the mass of the puck enough have any real influence on how much you could load the stick, you're probably shooting something that weighs over a couple of pounds. That isn't going to go very fast.


Agree to disagree I suppose.


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07-02-2010, 02:35 AM
  #23
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Quote:
Originally Posted by Razzmatazz View Post
That's why I added that last disclaimer. I think the maximum speed attainable would be with the real puck...there are a lot of variables in between that would determine one or the other....it is certainly easier to make the plastic puck go faster with less technique, but someone with great technique and a stiffer stick can probably get a lot more onto the real puck if they have the strength to flex the stick.
Well I will reiterate ... themz blue pucks used for little buggaboo leagues zip harder than the regular weighted black pucks.

They really do.

I shot a few last winter on an outdoor rink and the velocity was incredible.

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07-02-2010, 03:40 AM
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Quote:
Originally Posted by Hockeyfan68 View Post
Well I will reiterate ... themz blue pucks used for little buggaboo leagues zip harder than the regular weighted black pucks.

They really do.

I shot a few last winter on an outdoor rink and the velocity was incredible.
This! I used one of those blue pucks in practice last year, freaking thing was like a superball . I was hitting it so hard, it became misshapen. Now if only I could do that with a regulation puck....

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07-02-2010, 03:57 AM
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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...

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