How to make the weight float on water? [closed]

Question

The height of the cylinder is $3 \text { m }$ and the diameter is $45 \text { cm }$. The cylinder is filled with water. The block is of weight $30\ \text { kg }$ with dimensions $30\text { cm} \times \ 30 \text { cm} \times 30\text { cm} $. The block is put on the water's surface but it automatically sinks.

Please suggest some ways by which one can make the block float without changing the weight.

Can this be achieved without changing the dimensions of the cylinder?

Answer 1

Objects float when the volume of water they displace is less than the volume of the objects themselves. When objects sink, the volume of water they displace is greater than the volume of the object. The principle may seem relatively simple: Light objects float and heavy objects sink. However, you can make even heavy objects float by taking advantage of surface area and weight dispersal.

Another way to see this is from the point of view of densities. You can change the density of a substance by heating it, cooling it, or by adding something to it. If an object sinks in water, it’s because the object has a higher density than the water. There are two possible ways to make that object float, however:

1. Increase the density of the water so that the water becomes denser than the object. For example, an egg will usually sink in a glass of water, because it is denser than water. Adding salt to the water increases the density of the water, allowing the egg to float. This experiment also works with people, but you need a lot of salt (e.g the Dead Sea)

2. Increase the volume of the object so that the object becomes less dense than the water. A great example of this is ice floating in water. Ice is formed by freezing water. When it freezes, it increases in volume as the water molecules move farther apart to accommodate the lattice structure of ice. Because the ice is now less dense than water, it floats. This phenomenon also explains why ships float even though they are made of steel. A ship is built in such a way that it encloses large amounts of open space. The ship still displaces its weight in water, but because of the way the ship is constructed, it takes up more space than the volume of the water it displaces, so it floats.

Hope that answers your question.