Question

You put a steel plate on water. Would it sink or float? What would happen to a spoon?

Answer 1

Hint: The pressure exerted by an object on the water surface will decide if it floats or sinks in water. If the pressure exerted by the object due to its weight is large then it will break through the surface of water and sink but if pressure is less than it will manage to float on the surface of water.

Complete answer:
We are given a steel plate and a spoon. They are placed on the surface of water and we need to tell which one will float and which one will sink.
To answer this question, we need to first understand the concept of force exerted by the weight of an object per unit area which is known as pressure. Pressure exerted by an object is given as follows:
$P = \dfrac{F}{A}$
Here F is force exerted by the object due to its weight while A represents the surface area of the object.
When we talk about a steel plate, we know that it has a very large surface area. When it is placed carefully on the water surface then the pressure exerted by it on the water will be less because it has a large surface area. So, in spite of the fact that the steel plate is heavy, it will exert less pressure on the water surface and will not sink into water if it is placed carefully on the water surface.
When we talk about a spoon, then we know that it is lighter than a steel plate but the surface area of the spoon in contact with water will be less due to which the pressure exerted by the spoon will be larger than in case of steel plate. As a result, the spoon will sink into water.

Note:
It should be noted that even if an object is heavy, the pressure exerted by it will depend on the surface area of that body. A heavy body with a small surface area would have sunk into water but if we had a very light spoon like one made of plastic then it would have managed to float on the top of water.