Hockey Puck Physics

eepiccolo · 2003-07-14, 15:50

OK, we have two hockey pucks with the same initial velocity, both starting the same distance from the finish line, racing along a frictionless surface.

http://home.earthlink.net/~eepiccolo/images/puck.gif

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.

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The first puck is on a completely level surface. The second climbs down then up a hill on its way to the finish line, but finishes at the same height at which it started.

So the question is: who finishes first, or do they tie?

cheesehead · 2003-07-14, 16:13

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.

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Ya gotta give the diagram room to "breathe" (or else it smothers some of the following text or postings, at least as displayed by some browsers) -- like this:

Quote:

OK, we have two hockey pucks with the same initial velocity, both starting the same distance from the finish line, racing along a frictionless surface.

http://home.earthlink.net/~eepiccolo/images/puck.gif

.

.

.

.

.

.

The first puck is on a completely level surface. The second climbs down then up a hill on its way to the finish line, but finishes at the same height at which it started.

So the question is: who finishes first, or do they tie?

eepiccolo · 2003-07-14, 16:19

I see what you're saying. I've edited the original. But the problem still stands!

edit: Wait, I think I might not be seeing the same thing that others see. Does the picture actually cover up text in some browsers if the space isn't there?

cheesehead · 2003-07-14, 16:27

Your change was okay, until you stopped. As of the time I'm writing this, your image covers only about a third as much of the following text as it originally did. This font is tiny. Try adding two more dot-line, blank-line combinations.

eepiccolo · 2003-07-14, 16:36

Well, what I'm saying is, in IE 6.0 (what I use to browse), I don't need the filler lines to see everything. My suspicion is that in some other web browsers you need the space to see the main text. Is this true?

cheesehead · 2003-07-14, 16:39

Quote:

Originally Posted by eepiccolo

Well, what I'm saying is, in IE 6.0 (what I use to browse), I don't need the filler lines to see everything. My suspicion is that in some other web browsers you need the space to see the main text. Is this true?

Yes. I'm using an "older" browser.

eepiccolo · 2003-07-14, 16:43

OK, now I understand. So the rule of thumb should be to put at least as much space under the picture as the height of the picture itself. I'll fix that right now.

So, anyway, Which puck wins, or do they tie?

:D

cheesehead · 2003-07-14, 16:47

Back to the puzzle --

If there's no surface or air friction, they tie.

Maybe if the hill configuration is such that the second puck tumbles ... but if you additionally specify that the puck material is perfectly elastic, and Newtonian mechanics hasn't changed in 35 years, it still looks like a tie to me.

Edit: Oh, wait - I guess the second puck wins because the additional vertical momentum gets transferred to horizontal momentum even without friction, which I originally thought was necessary. Gee, I'm rusty.

Edit edit: Er ... we're assuming this is not a zero-g situation, aren't we. In zero-g, they tie.

eepiccolo · 2003-07-14, 16:52

I won't say whether you're right or wrong, chessehead, but I will clarify that the puck does not tumble, the shape of the hill is irrelevant, and no energy is lost through "collisions" with the hills.

edit: This was a reply to your original, unedited post, cheesehead. And yes, there is gravity.

cheesehead · 2003-07-14, 17:04

Rust never sleeps. I do, but I've never played hockey or even ice-skated.

The very first day I ever lived in a climate where lakes routinely freeze over each winter, the very first thing I saw on TV was a picture of a house partly submerged after breaking through the ice while it was being moved over a frozen lake. I concluded that the engineering of traveling on top of frozen water had not yet reached the level of reliability I would require before trying to do so on the skinny edge of a blade.

eepiccolo · 2003-07-14, 17:13

Does anybody else want to weigh-in on the problem before I give cheesehead his verdict?

2003-07-14, 15:50	#1
eepiccolo Dec 2002 Frederick County, MD 562₈ Posts	Hockey Puck Physics OK, we have two hockey pucks with the same initial velocity, both starting the same distance from the finish line, racing along a frictionless surface. http://home.earthlink.net/~eepiccolo/images/puck.gif . . . . . The first puck is on a completely level surface. The second climbs down then up a hill on its way to the finish line, but finishes at the same height at which it started. So the question is: who finishes first, or do they tie?

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2003-07-14, 16:19	#3
eepiccolo Dec 2002 Frederick County, MD 2·5·37 Posts	I see what you're saying. I've edited the original. But the problem still stands! edit: Wait, I think I might not be seeing the same thing that others see. Does the picture actually cover up text in some browsers if the space isn't there?

2003-07-14, 16:27	#4
cheesehead "Richard B. Woods" Aug 2002 Wisconsin USA 7692₁₀ Posts	Your change was okay, until you stopped. As of the time I'm writing this, your image covers only about a third as much of the following text as it originally did. This font is tiny. Try adding two more dot-line, blank-line combinations.

2003-07-14, 16:36	#5
eepiccolo Dec 2002 Frederick County, MD 562₈ Posts	Well, what I'm saying is, in IE 6.0 (what I use to browse), I don't need the filler lines to see everything. My suspicion is that in some other web browsers you need the space to see the main text. Is this true?

2003-07-14, 16:43	#7
eepiccolo Dec 2002 Frederick County, MD 2×5×37 Posts	OK, now I understand. So the rule of thumb should be to put at least as much space under the picture as the height of the picture itself. I'll fix that right now. So, anyway, Which puck wins, or do they tie? :D

2003-07-14, 16:47	#8
cheesehead "Richard B. Woods" Aug 2002 Wisconsin USA 17014₈ Posts	Back to the puzzle -- If there's no surface or air friction, they tie. Maybe if the hill configuration is such that the second puck tumbles ... but if you additionally specify that the puck material is perfectly elastic, and Newtonian mechanics hasn't changed in 35 years, it still looks like a tie to me. Edit: Oh, wait - I guess the second puck wins because the additional vertical momentum gets transferred to horizontal momentum even without friction, which I originally thought was necessary. Gee, I'm rusty. Edit edit: Er ... we're assuming this is not a zero-g situation, aren't we. In zero-g, they tie.

2003-07-14, 16:52	#9
eepiccolo Dec 2002 Frederick County, MD 2×5×37 Posts	I won't say whether you're right or wrong, chessehead, but I will clarify that the puck does not tumble, the shape of the hill is irrelevant, and no energy is lost through "collisions" with the hills. edit: This was a reply to your original, unedited post, cheesehead. And yes, there is gravity.

2003-07-14, 17:04	#10
cheesehead "Richard B. Woods" Aug 2002 Wisconsin USA 1111000001100₂ Posts	Rust never sleeps. I do, but I've never played hockey or even ice-skated. The very first day I ever lived in a climate where lakes routinely freeze over each winter, the very first thing I saw on TV was a picture of a house partly submerged after breaking through the ice while it was being moved over a frozen lake. I concluded that the engineering of traveling on top of frozen water had not yet reached the level of reliability I would require before trying to do so on the skinny edge of a blade.

2003-07-14, 17:13	#11
eepiccolo Dec 2002 Frederick County, MD 2·5·37 Posts	Does anybody else want to weigh-in on the problem before I give cheesehead his verdict?