**Introduction:**

Pressure is defined as the force applied per unit area. It is a measure of how much force is distributed over a given area. In this scenario, we are given the mass of a boy and the dimensions of a wooden block on which he stands. We need to calculate the pressure exerted by the boy on the wooden block.

**Given:**

Mass of the boy (m) = 45 kg
Side of the wooden block (a) = 50 cm = 0.5 m

**Calculating the force:**

To calculate the pressure, we first need to calculate the force exerted by the boy on the wooden block. The force can be determined using Newton's second law of motion, which states that force (F) is equal to the product of mass (m) and acceleration (a).

Since the boy is standing still on the wooden block, the acceleration is zero, and therefore, the force exerted by the boy is also zero.

**Calculating the pressure:**

As the force exerted by the boy is zero, we can conclude that the pressure exerted by the boy on the wooden block is also zero.

**Conclusion:**

The pressure exerted by the boy on the wooden block is zero. This is because the force exerted by the boy is zero, as he is standing still on the block. Therefore, there is no pressure being applied by the boy on the wooden block.