Fill a glass bowl with water to about three-quarters full. Place the cork in the water. It doesn’t sink, but floats on top of the water.
Remove the cork from the water and insert a 1-inch nail into the base of the wine cork. Push the nail about 1/2 inch into the cork using your fingers. Cork is very soft, so it’s easy to insert the nail.
Put the cork and nail into the water. Look at the difference in how the cork is floating. It still doesn’t sink, but it’s lower in the water. This is because the weight of the nail has increased the gravitational pull, but is still not heavy enough to overcome the upward pressure.
Remove the cork from the water and insert another 1 inch nail into the cork next to the first one. Put the cork back into the water. The cork may still float, or it may sink. It all depends on the size of the cork and the weight of the nails.
Continue to insert nails into the cork one at a time, if the cork hasn’t already sunk. You can experiment to see the difference in the time it takes for the cork to sink to the bottom. The more nails you insert into the cork, the heavier the gravitational pull and therefore the faster the cork sinks.