  Now here's a ride that you'd want to pay extra for! Just why do those swans float, anyway? They must weigh a thousand pounds, for heaven's sake! Not to mention all those people sitting in them. The secret is in making sure the density of the boat and passengers is less than the density of water, which is 1 gram per cubic centimetre. Any substance immersed in water that has a density less than this will experience a buoyant force upwards. Density is calculated by dividing mass by volume. If the boat were made from a solid material, it might not float. But it contains a lot of styrofoam underneath, which is light (it's full of air pockets). This helps to lower its mass. The swan is still pretty heavy, though. But it has a large volume. When you divide its mass (in grams) by its volume (in cubic centimetres), the answer will be less than 1. So it will float on water. This is also the reason that large steel ships, like aircraft carriers, that weigh a gazillion tonnes, can float. They have a lot of empty space inside, and a large volume. So when you divide their large mass by their volume, you're dividing by an even larger number ... and the answer will be less than 1. So the boat floats! |