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Old 13-01-2012, 15:51   #61
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Re: Anchor Riddle

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Originally Posted by cwyckham View Post
Folks, the weight of the anchor does not change when it goes in the water. It still weighs the same, it just now also has an additional buoyancy force on it. It's the same with the boat. The boat doesn't weigh nothing just because the buoyancy and weight forces cancel eachother out.

The boat and anchor as a system have a weight which is counteracted exactly by the bouyancy force, whether the anchor is in the water or not. Only once the anchor touches the ground that a third force (normal force from the ground up on the anchor) is added and the bouyancy force is decreased, decreasing the amount of water displaced by the boat.
EXACTLY.

Now, those that want some MORE pictures - what EXACTLY do you want me to do?

Note that there ARE pictures at the bottom of Page 3 of this thread.
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Old 13-01-2012, 15:57   #62
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Re: Anchor Riddle

Bill,

Must be computer differences. Your last post on my computer is the bottom of page 2.
I'd like to see your glass pic again with the balls suspended on string and another set of pics with a wood anchor on and off the boat.

All that in your spare time of course!

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Old 13-01-2012, 16:10   #63
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Re: Anchor Riddle

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Bill,

Must be computer differences. Your last post on my computer is the bottom of page 2.
I'd like to see your glass pic again with the balls suspended on string and another set of pics with a wood anchor on and off the boat.

All that in your spare time of course!

I'll see if I can get it done.

What's with a WOODEN anchor that floats? I'm thinking that with the ball bearings, they might be too dense to show a difference. I might try some combination.
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Old 13-01-2012, 16:28   #64
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Re: Anchor Riddle

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Originally Posted by bstreep View Post
EXACTLY.

Now, those that want some MORE pictures - what EXACTLY do you want me to do?

Note that there ARE pictures at the bottom of Page 3 of this thread.
I think we need to model three different anchor types: a steel ball bearing to model a typical anchor, an aluminum ball bearing to model a fortress, and wadded up bubble gum wrappers to model a rocna
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Old 13-01-2012, 17:43   #65
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Re: Anchor Riddle

OK, once more. The setup: This time I'm using magnetic tubes. In order to balance the "boat" I needed a "keel", which is two of the tubes.



Anchor is on the boat:



Anchor under the boat, but still attached (hanging on the keel). Note NO difference in the water level, but the "boat" sits higher in the water. I didn't really expect that, for some reason. But it makes sense...:



Anchor is on the bottom. Note water level in the "tank" is lower and the boat floats WAY higher:



P.S. I noticed that it might look like there's a minor difference between in/under the "boat". I just re-did it, and it's due to the angle of the shot - the thickness of the glass makes it look slightly different, but I assure you, it isn't.
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Old 13-01-2012, 17:53   #66
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Re: Anchor Riddle

Same angles, in and under. I'm supposed to be getting ready to go out to dinner for our anniversary...



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Old 13-01-2012, 19:24   #67
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Re: Anchor Riddle

The last experiment shows reality--when the anchor enters the water, it displaces an amount of water equal to its volume. As Archimedes found, the anchor weighs less under water by the weight of the water it displaces. Thus, the boat and anchor weigh less and the boat floats a little higher. The total of boat and anchor still displace the same amount, so the water level stays the same until the anchor hits the bottom.

You can understand this a bit better by jumping off your boat, swimming to the bow, and pulling yourself up on the anchor chain. You are nearly the same density as water, so when you are nearly submerged there is very little pull on your arms. However as you climb the anchor chain the pull increases until your entire weight is carried by the boat when you clear the water--the same weight the boat would carry if you were standing on the bow.
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Old 13-01-2012, 20:03   #68
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Re: Anchor Riddle

Archimedes Principle: An object fully or partially emersed in a liquid is bouyed up by a force equal to the wieght of the water it displaces.

This answer has 3 facets to consider:
1. Weight of chain and anchor
2. displacement of chain and anchor
3. weight of anchor alone

On the boat the weight of chain and anchor add to the displacement of the boat, if the anchor and chain go overboard and the anchor rests on bottom then the wieght of the chain is still adding to the displacement of the boat so you can only subtract the weight of the anchor if its resting on bottom.

The volume of water that the chain and anchor displaces together is less than its weight thereby causing it to sink...so, the weight of the anchor alone is greater than its displacement thereby causing the rise of the boat to be greater than the volume displaced by the chain and anchor.

The boat level will rise and the water level will fall.
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Old 13-01-2012, 20:10   #69
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Re: Anchor Riddle

To add to my last post, until the anchor reaches bottom, the water level rises because the boat still has the weight of the gear pulling on it and the water is displaced by the addition of the hardware. Once the anchor touches bottom then the weight of the anchor is the only part that is eliminated from the original displacement of the boat.
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Old 13-01-2012, 20:16   #70
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Re: Anchor Riddle

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To add to my last post, until the anchor reaches bottom, the water level rises because the boat still has the weight of the gear pulling on it and the water is displaced by the addition of the hardware. Once the anchor touches bottom then the weight of the anchor is the only part that is eliminated from the original displacement of the boat.
Before the anchor touches the bottom, the water level stays the same in the tank. The total weight of the boat/anchor system stays the same, so the amount of displaced water is the same, so the water level in the tank stays the same.

The boat will float higher because some of the water is now being displaced by the anchor, but the total amount of displaced water is the same, so the boat must be displacing less water.
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Old 13-01-2012, 20:25   #71
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The anchor under water has equal mass, but weighs less than when aboard. When you hang it overboard but above water it will weigh (pull on the rode with) say 100lb but as soon as it submerges it becomes 85lb or so, meaning the boat will go up a bit.

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Old 13-01-2012, 21:00   #72
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Re: Anchor Riddle

Bill,
Happy Anniversary and thanks for the pics!
I hope your wife appreciates your dedication to the thread.
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Old 14-01-2012, 03:26   #73
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Re: Anchor Riddle

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OK, once more. The setup: This time I'm using magnetic tubes. In order to balance the "boat" I needed a "keel", which is two of the tubes. .
And thus empirical science is born.

Now we have that one sorted out do you think you could have a quick look at cold fusion?
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Old 14-01-2012, 03:34   #74
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Re: Anchor Riddle

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Originally Posted by Borealis View Post

The volume of water that the chain and anchor displaces together is less than its weight thereby causing it to sink...so, the weight of the anchor alone is greater than its displacement thereby causing the rise of the boat to be greater than the volume displaced by the chain and anchor.

The boat level will rise and the water level will fall.
http://www.cruisersforum.com/forums/...tml#post860164


Scientific experiment has shown your analysis to be wrong

A cube of size 10 and twice the density of water will "weigh" 5 under water and displace 5, total displacement if it is being suspended is the same. Theory matches experiment. Lets move on to those faster than the speed of light nuetrinos - any ideas anyone?
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