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06-08-2013, 04:21 PM   #31
john4200
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Quote:
 Originally Posted by jeff92k7 Keep in mind that with forward momentum, there will be a higher pressure area on the front of the spinning wheel and a lower pressure area on the back of the spinning wheel. Thus, the downward motion at the front of the powered, spinning wheel can create more traction and lift against the water than the drag created by the upward motion of the rear of the wheel.
Except that you have not considered the additional downward force created by the wheel throwing some of the water upwards.

I repeat, this question cannot be settled just by looking at it. The forces are too complicated to analyze by simple physics. The way to settle the question is to do the experiment.

06-08-2013, 11:24 PM   #32
verdugan
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Quote:
 Originally Posted by alpacaboy Something disturbs me about seeing Buster referred to as "it." My reaction was something like, "How mean. Buster's a 'him'. A distinct part of the Mythbusters crew. He has feeli... no, wait. Oh yeah, I guess LoadStar's right." But it still bothers me.
Do you cry when you see what they do to "him" during the episodes?

06-10-2013, 03:07 PM   #33
jeff92k7
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Quote:
 Originally Posted by john4200 Except that you have not considered the additional downward force created by the wheel throwing some of the water upwards. I repeat, this question cannot be settled just by looking at it. The forces are too complicated to analyze by simple physics. The way to settle the question is to do the experiment.
I did consider that and even mentioned that when I said "drag created by the upward motion of the rear of the wheel". Though, granted, I didn't use the specific words "throwing the water upwards". I would have thought that would have been clear by my statement, but I guess I have to spell it out for some people.

I stand by my statement. The higher pressure in the front would provide greater traction than any drag caused in the low pressure area at the rear of the wheel INCLUDING any water being thrown upwards. The water being pushed downwards will far exceed the water being thrown upwards.

Jeez, this is a touchy bunch here.

As for doing the experiment, I thought they proved it pretty well by traveling around 300+ feet (yards?) across the water. If it was solely a "rock skipping" effect, it would have worn off early. It was clear (at least on my TV), that the only reason they couldn't continue was because of a loss of momentum/buoyancy of the front wheel. Once it "dug into" the water, they weren't going any farther. The front wheel stayed up due to it's rolling motion. Once it stopped/slowed, it went under. The powered rear wheel was still spinning and lifting the rear out of the water.

Of course, discussions like this are why I don't hang out on the mythbusters forums. It's an entertaining show with a little bit of science thrown in. Once you start to over analyze the science, it loses all the entertainment value and we end up with people arguing about it on internet forums.

I think I'll exit this thread now and go laugh at the people who are still shocked by the red wedding.

06-10-2013, 03:23 PM   #34
Hank
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Quote:
 Originally Posted by jeff92k7 Jeez, this is a touchy bunch here.
Welcome to TCF. But don't let that scare you off.

06-10-2013, 04:36 PM   #35
john4200
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Quote:
 Originally Posted by jeff92k7 I did consider that and even mentioned that when I said "drag created by the upward motion of the rear of the wheel". Though, granted, I didn't use the specific words "throwing the water upwards". I would have thought that would have been clear by my statement, but I guess I have to spell it out for some people.
Actually, I guess you need to not get the physics incorrect. Drag is not equal to the force required to throw water up. Talking about two different pressures as definitive in determining drag or force on the wheel is absurd when the pressures around the wheel vary greatly with position.

Your hand-waving analysis would apply equally well to a paddlewheel in the air. So, do you also claim that if you spin a paddlewheel fast enough in the air that it will climb into the sky? Where are the paddlewheel airplanes?

 06-10-2013, 06:04 PM #36 Kamakzie Are you serious bro?     Join Date: Jan 2004 Location: MI Posts: 4,996 I would've liked to see them have the stunt guy try to cross the whole lake instead of Jamie.. __________________ HR-20 x 2 HR-21 x 2
06-10-2013, 07:11 PM   #37
phox_mulder
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Quote:
 Originally Posted by Kamakzie I would've liked to see them have the stunt guy try to cross the whole lake instead of Jamie..
This.

He seemed to be able to keep the front wheel out of the water more than Jamie was.
Not to mention the difference in weight.

phox

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06-10-2013, 07:11 PM   #38
randyb359
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Quote:
 Originally Posted by john4200 Actually, I guess you need to not get the physics incorrect. Drag is not equal to the force required to throw water up. Talking about two different pressures as definitive in determining drag or force on the wheel is absurd when the pressures around the wheel vary greatly with position. Your hand-waving analysis would apply equally well to a paddlewheel in the air. So, do you also claim that if you spin a paddlewheel fast enough in the air that it will climb into the sky? Where are the paddlewheel airplanes?
The front of the wheel pushes the water out of its way so there is much less for the rear of the wheel to push on so the front pushing down will have a greater affect because it is pushing on more water

06-10-2013, 07:17 PM   #39
john4200
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Quote:
 Originally Posted by randyb359 The front of the wheel pushes the water out of its way so there is much less for the rear of the wheel to push on so the front pushing down will have a greater affect because it is pushing on more water
Very funny. You should get a job doing physics standup comedy.

06-11-2013, 07:58 AM   #40
jeff92k7
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Quote:
 Originally Posted by john4200 So, do you also claim that if you spin a paddlewheel fast enough in the air that it will climb into the sky? Where are the paddlewheel airplanes?
That is utterly ridiculous and not even comparable. Are you seriously trying to compare a motorcycle wheel getting traction from a small patch of water, lifting it up into a lower pressure field (the air) with a device completely inside only one gaseous field (air)????

By your logic, astronauts don't need spacecraft. They can just waive their arms to move around in space. Apparently the need for, and effects of, an atmosphere are irrelevant.

06-11-2013, 11:20 AM   #41
john4200
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Quote:
 Originally Posted by jeff92k7 That is utterly ridiculous and not even comparable.
Just as ridiculous as a motorcycle wheel climbing water, and exactly comparable when the only justification is the vague, handwaving explanation that has been given for the water wheel climbing.

I'm surprised you do not know that the pressure in the air varies with altitude. Both water and air behave as fluids in these conditions, and both have the pressure vary with depth/height.

I repeat, the physics of the problem is too complicated to be settled by just a vague, hand-waving explanation. The way to settle it is to do an experiment. I have sent the mythbusters a note asking about it. I guess the more notes they receive, the more likely they are to look into it.

 06-11-2013, 11:29 AM #42 pmyers Registered User     Join Date: Jan 2001 Location: Gilbert, AZ Posts: 14,856 Jeff fell into the trap....lol
06-11-2013, 11:51 AM   #43
john4200
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Quote:
 Originally Posted by pmyers Jeff fell into the trap....lol
But does he have a flying wheel that can climb out of it?

06-11-2013, 01:53 PM   #44
jeff92k7
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Quote:
 Originally Posted by pmyers Jeff fell into the trap....lol
Ha ha. I should have stuck with my earlier statement about not coming back to this thread. I'm not going to bother responding to John's latest response. It's clear that I'm not communicating my knowledge of physics very well. I'd rather go beat my head against a wall. I'd get a more educated response from it than I am getting from John.

Carry on. I'll laugh at everyone's responses and opinions from a distance.

Last edited by jeff92k7; 06-11-2013 at 02:31 PM.

06-11-2013, 02:08 PM   #45
john4200
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Quote:
 Originally Posted by jeff92k7 It's clear that I'm not communicating my knowledge of physics very well.
Your communication is fine, it is the actual physics knowledge that is lacking.

06-11-2013, 02:52 PM   #46
pmyers
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Quote:
 Originally Posted by jeff92k7 Ha ha. I should have stuck with my earlier statement about not coming back to this thread. ...Carry on. I'll laugh at everyone's responses and opinions from a distance.
It only took me 10K+ posts to figure that out

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