Displacement question.

[RED-DOG]

I don't like that video. There are too many different variables for a straight comparison, solid objects, hollow objects all act different. The reason a ship doesn't sink is not because steel is lighter than water it's because the shape of the ship. If you melted a ship down and moulded it into a solid block it would sink.

Correct. And if you inflated Celtic to the size of a barrage balloon he would float in less water.

[bobAlike]

But that's about the shape again and not the weight. Try this at home- get a saucer and place it on top of a sink full of water, if you did this carefully and no water got on to the top of the saucer it has a good chance to float. Now while the saucer is floating poor some water on top of the saucer. Chances are that it will sink. The same goes for a concrete barge or steel ship.

If the density of the polystyrene molecules hasn't changed then it would still float.

[RED-DOG]

But that's about the shape again and not the weight. Try this at home- get a saucer and place it on top of a sink full of water, if you did this carefully and no water got on to the top of the saucer it has a good chance to float. Now while the saucer is floating poor some water on top of the saucer. Chances are that it will sink. The same goes for a concrete barge or steel ship.

If the density of the polystyrene molecules hasn't changed then it would still float.

But Celtic is denser than polystyrene. How can 8lbs of water float him?

[RED-DOG]

If you filled some wellies up with water and he put them on, would he float?

[EvilPie]

If it helps.....

This is all about volume and density.

Celtic and water are equally as dense (in more ways than one)

Therefore it becomes about weight.

[teamonkey]

Red,

he would float

i promise

not too sure how i can explain this though so that you'd get it

remember, the longer we discuss this, the more nando's celtic will consume

[EvilPie]

This stopped me going to sleep!!

I am wrong; if the bath was shaped correctly, taking into account the shape of Celtic while suspended in water, then yes, he could indeed float in a very small amount of water.

The reason for this is that his body will have effectively displaced the water by occupying the space the water would have been in.

I'm not sure of the exact minimum amount or thickness of the water layer required between Celtic and the bath wall, but I imagine theoretically he could float on less than a couple of mm of water.

He'd still get wet and cross at your experiments during his bath time

No. He wouldn't float unless the water he displaced was heavier than he was.

Unless the bath is big enough to hold his weight in water without it spilling over the edge when he gets in, he cant float.

Sorry Red, he will still float.

Best way to think about this is instead of something odd shaped like celtic, use something regular shaped like a cube, now for an object to float its density must be less than the medium it is floating in, so a cube of some non permeable plastic will do this, if the cube is 10x10x10 cm, when floating in the water 1cm is above the water level.

Put said cube into a full bath of water, Where it will float, with, as said before,  1cm showing, so it has displaced 10x10x9 cm of water. Measure this amount of water, which will be 900cubic cm of water.

Now take a bath that measures 11x11x10 cm, and fill in to the brim again with water. This time when you put the cube in the bath, you will see that it also floats, with the same 1cm showing out of the water, so again it has displaced the same volume of water, ie 10x10x9cm =900 cubic cm.

Repeat the experimeny by slowly making the bath smaller and you will see that an object will float in a very small amount of water indeed.

Substitute the regular shaped object and bath for celtic, repeat experiment, and you will find that celtic will float, and be hungry at the same time

Now, whats your thoughts on Schroedingers celtic, where if celtic and a plate of nandos chicken are placed in a box, the chicken could be both eaten AND untouched at the same time!

Sorry but this won't work. There is sufficient water in your 11x11x10 bath but as soon as you put your 10x10x10  cube in it the water will start to spill over the sides and no longer be able to provide any downwards force against the cube.

For this to work you'd need the bath to have a volume of 1900 cm cubed then you'd have your 1cm of cube poking out the top. Any smaller and I'm afraid that cube is going down......

[EvilPie]

Red,

he would float

i promise

not too sure how i can explain this though so that you'd get it

remember, the longer we discuss this, the more nando's celtic will consume

If this is true then it must also be true that if we make the bath sufficiently snug Celtic will float on air.

Your floaty example seems to be relying on something other than displacement such as friction. If Celtic can prevent the small amount of water from escaping from underneath him then yes he will float but as soon as it leaves the bath and can't act downwards against him he's sinking.

[bobAlike]

All the debating is really quite interesting but there is one thing that is missing - Does Celtic ever have a bath?

[EvilPie]

I'm not sure this counts as debating.

Would this be a debate:

"2 + 2 = 5"

"2 + 2 =  4"

"2 + 2 = 4 and a little bit then...."

"Nope it's still 4"

[teamonkey]

This stopped me going to sleep!!

I am wrong; if the bath was shaped correctly, taking into account the shape of Celtic while suspended in water, then yes, he could indeed float in a very small amount of water.

The reason for this is that his body will have effectively displaced the water by occupying the space the water would have been in.

I'm not sure of the exact minimum amount or thickness of the water layer required between Celtic and the bath wall, but I imagine theoretically he could float on less than a couple of mm of water.

He'd still get wet and cross at your experiments during his bath time

No. He wouldn't float unless the water he displaced was heavier than he was.

Unless the bath is big enough to hold his weight in water without it spilling over the edge when he gets in, he cant float.

Sorry Red, he will still float.

Best way to think about this is instead of something odd shaped like celtic, use something regular shaped like a cube, now for an object to float its density must be less than the medium it is floating in, so a cube of some non permeable plastic will do this, if the cube is 10x10x10 cm, when floating in the water 1cm is above the water level.

Put said cube into a full bath of water, Where it will float, with, as said before,  1cm showing, so it has displaced 10x10x9 cm of water. Measure this amount of water, which will be 900cubic cm of water.

Now take a bath that measures 11x11x10 cm, and fill in to the brim again with water. This time when you put the cube in the bath, you will see that it also floats, with the same 1cm showing out of the water, so again it has displaced the same volume of water, ie 10x10x9cm =900 cubic cm.

Repeat the experimeny by slowly making the bath smaller and you will see that an object will float in a very small amount of water indeed.

Substitute the regular shaped object and bath for celtic, repeat experiment, and you will find that celtic will float, and be hungry at the same time

Now, whats your thoughts on Schroedingers celtic, where if celtic and a plate of nandos chicken are placed in a box, the chicken could be both eaten AND untouched at the same time!

Sorry but this won't work. There is sufficient water in your 11x11x10 bath but as soon as you put your 10x10x10  cube in it the water will start to spill over the sides and no longer be able to provide any downwards force against the cube.

For this to work you'd need the bath to have a volume of 1900 cm cubed then you'd have your 1cm of cube poking out the top. Any smaller and I'm afraid that cube is going down......

no no no

in both examples of mine, the same amount of water is displaced

the volume of the cube in the water is 10x10x9

therefore the volume displaced by the cube is always going to be 10x10x9

that volume will not change no matter how big the bath is provided that bath itself is larger than 10x10x9

no substitue the cube for celtic, and change the shape of the bah from a cube to a "celtic" and you will see that i am right

it's not about how much water is still in the bath, its about how much water the item, ie celtic, displaces, if there is still water in the bath and the "celtic" is not touching any surfaces, then he is floating

[EvilPie]

I guess 2 + 2 is 5 then.

[teamonkey]

which part am i not explaining properly?

[EvilPie]

no no no

in both examples of mine, the same amount of water is displaced

the volume of the cube in the water is 10x10x9

therefore the volume displaced by the cube is always going to be 10x10x9

that volume will not change no matter how big the bath is provided that bath itself is larger than 10x10x9

no substitue the cube for celtic, and change the shape of the bah from a cube to a "celtic" and you will see that i am right

it's not about how much water is still in the bath, its about how much water the item, ie celtic, displaces, if there is still water in the bath and the "celtic" is not touching any surfaces, then he is floating

So what if you take your 11 x 11 x 10 bath and only half fill it with water meaning that there's only 605cm cubed available to be displaced.

Will your 10x10x10 float now that there isn't 900cm cubed available to be displaced in the first place?

[EvilPie]

which part am i not explaining properly?

The factual bit