# So if I had a canoe floating in the water on earth it would sink lets

1. Jul 28, 2011

### cragar

So if I had a canoe floating in the water on earth it would sink lets say 4 inches down. Now I take that same canoe with the same mass and put it in a lake on the moon, suppose the moon had a lake . Wouldn't the canoe also sink 4 inches down on the moon . Assuming the canoe had the same mass and was in water both times. And I was wondering could their ever be a Gravitational field where it was strong enough to sink the canoe besides a black hole. Will the canoe sink the same depth in all G fields.

2. Jul 29, 2011

### SteamKing

Staff Emeritus
Re: Buoyancy

What happens when bodies float? Apply Archimedes principle here.

3. Jul 29, 2011

### Bloodthunder

Re: Buoyancy

Continuing on from SteamKing, Archimedes' Principle is "Any object, wholly or partially immersed in a fluid, is buoyed up by a force equal to the weight of the fluid displaced by the object."

Note the word "weight", which is mass times gravitational field strength.

4. Jul 29, 2011

### cragar

Re: Buoyancy

ok i understand Archimedes principle, Suppose we had a really strong G field, like on Jupiter, Isn't Jupiter G field so strong that if a can was placed on its surface that it would be crushed. Im just wondering if there is some wierd extreme case where it would pull the boat in, probably not though

5. Jul 29, 2011

### Bloodthunder

Re: Buoyancy

I don't think the gravitational field strength would matter.
Weight of boat is buoyed up by a force equal to weight of fluid displaced.
So W_boat = W_water.
Since W = mg and g is same in both cases, m_boat = m_water.
In that case, there would never be a situation where the boat would be sunk. The water level outside the boat would probably always be at the same level.

6. Nov 11, 2011

### Doomemperor

Re: Buoyancy

The Gravitational force would not matter, because it is acting on not only your canoe-but on the water as well. Keep in mind that Buoyancy is the counter-force of gravity.

7. Nov 11, 2011

### Staff: Mentor

Re: Buoyancy

No, you missed what Archimedes principle says here: The weight of the canoe increases at exactly the same proportion as the weight of the water increases, so the canoe floats at exactly the same height/depth everywhere.

8. Nov 11, 2011

### Naty1

Re: Buoyancy

You can verify Watters post via a simple thought experiment:use the equivalence principle: accelerate a body of water with a canoe floating on top.....F = Ma applies to all and the float level remains the same...

9. Nov 11, 2011

### cragar

Re: Buoyancy

ok i get it, thanks for your posts