In my lifetime I have seen many balloons floating up into the sky... But where do they go?

I have been taught that acceleration due to gravity is affected by surface area and not mass. I still find it hard to believe that a situation like in my question would be possible?

I know the air inside the lungs makes people float and just like that,the air inside a ship decreases the density of the total volume and hence makes the ship float.But what happens if you vacuum the air inside the ship and then seal it somehow,just like exhaling air from your lungs,does the ship sink cause the density of the total volume will just be the density of them metals inside the ship despite the airless big space in it?

If you sink an object and then let go then it accelerates upwards. What if I sank something a very long way (say a mile or so)?

I've read in New Scientist about the potential of using supercavitation to travel very fast through water.

So what’s to stop me attaching a lightweight projectile onto a big rock with a piece of string which will detach at a certain depth, dropping it off a boat and firing something into space?

I have never been able to float very well, often after a matter of seconds my stomach caves in and i sink.  Recently on a hot day I had several beers before floating in my backyard pool.  I could suddenly float.

Why?  Is it something to do with the beer in my stomach or blood or simply me being more relaxed and thus making it easier to float?

Having discovered the joys of the "appletini" (vodka mixed with apple juice, cider or apple liquor) I have a question.

The garnish is a slice of apple and a Maraschino or glacé cherry on a cocktail stick. If the cherry is at the bottom of the stick it floats in the appletini, but with the apple slice at the bottom it sinks. Why? Surely the buoyancy of the two items combined is an absolute and their orientation should make no difference.

I shall leave it to the imagination as to the amount of 'tinis consumed before this anomaly became a burning conversation topic!

Richard Batho, St Saviour, Jersey

In my local store there is an interesting drink advertisement; a machine with two circular discs, one at the bottom and one at the top, seems to make a can of drink levitate and rotate so that customers can see the whole label. I think the machine uses electromagnets to do this, but I am still curious about it because the can never moves vertically - only slightly horizontally, and forwards and backwards. I tried removing the can once and the can didn't float when I replaced it. How does this work and how does the machine achieve such a precise region of movement for the can?

Some friends and I were drinking from a jug of water that contained wedges of both lime and lemon. All the lemon wedges were floating, but all the lime wedges had sunk to the bottom of the jug.

There were enough pieces of both for us to infer this was not just coincidence, and all of us were pretty certain that we'd seen lime slices floating before. Can anyone offer an explanation?

Bladon Mooney, Leicester, UK

Thanks to the anonymous correspondent who sent a link to a page on the Steve Spangler Science site, where the answer is tested - Ed

(Image: tellgraf, stock.xchng)